bluuebunny/crossref_metadata_2025 huggingface dataset:
Overlapping hand-over-hand mechanism of single molecular motility of cytoplasmic dynein
Authors: Toba Shiori , Watanabe Tomonobu M. , Yamaguchi-Okimoto Lisa , Toyoshima Yoko Yano , Higuchi Hideo
Published: April 2006

Structural differences between dynein and kinesin suggest a unique molecular mechanism of dynein motility. Measuring the mechanical properties of a single molecule of dynein is crucial for revealing the mechanisms underlying its movement. We measured the step size and force produced by single molecules of active cytoplasmic dynein by using an optical trap and fluorescence imaging with a high temporal resolution. The velocity of dynein movement, 800 nm/s, is consistent with that reported in cells. The maximum force of 7–8 pN was independent of the ATP concentration and similar to that of kinesin. Dynein exhibited forward and occasional backwards steps of ≈8 nm, independent of load. It is suggested that the large dynein heads take 16-nm steps by using an overlapping hand-over-hand mechanism.
Experimental evidence for interspecific directional selection on moth pheromone communication
Authors: Groot Astrid T. , Horovitz Joy L. , Hamilton Jennifer , Santangelo Richard G. , Schal Coby , Gould Fred
Published: April 2006

The chemical composition of the sexual communication signals of female moths is thought to be under strong stabilizing selection, because females that produce atypical pheromone blends suffer lower success in finding mates. This intraspecific selection pressure cannot explain the high diversity of moth pheromone blends found in nature. We conducted experiments to determine whether communication interference from males of closely related species could exert strong enough directional selection to cause evolution of these signals. Attraction and mating success ofHeliothis subflexa(Hs) females with a normal quantitative trait locus for production of acetate pheromone components (norm-OAc) were compared with Hs females with an introgressed quantitative trait locus fromHeliothis virescens(Hv) that dramatically decreased the amount of acetate esters in their pheromone glands (low-OAc). In field experiments with natural Hv and Hs populations, 10 times more Hv males were captured in traps baited with live low-OAc Hs females than in traps with norm-OAc Hs females. This pattern was confirmed in mate-choice assays in cages. Hybrids resulting from Hv–Hs matings have effectively zero fitness in the field. Combining our results with the extensive data set gathered in the past 40 years on the reproductive biology of Hv, we can quantitatively estimate that the directional selection exerted by Hv males on Hs females to produce relatively high amounts (>5%) of acetates can range from 0.135 to 0.231. Such intense interspecific selection may counteract intraspecific stabilizing selection that impedes evolutionary changes in pheromone blends and could lead to diversification of sexual signals.
Natural selection and molecular evolution in primatePAX9gene, a major determinant of tooth development
Authors: Pereira Tiago V. , Salzano Francisco M. , Mostowska Adrianna , Trzeciak Wieslaw H. , Ruiz-Linares Andrés , Chies José A. B. , Saavedra Carmen , Nagamachi Cleusa , Hurtado Ana M. , Hill Kim , Castro-de-Guerra Dinorah , Silva-Júnior Wilson A. , Bortolini Maria-Cátira
Published: April 2006

Large differences in relation to dental size, number, and morphology among and within modern human populations and between modern humans and other primate species have been observed. Molecular studies have demonstrated that tooth development is under strict genetic control, but, the genetic basis of primate tooth variation remains unknown. ThePAX9gene, which codes for a paired domain-containing transcription factor that plays an essential role in the development of mammal dentition, has been associated with selective tooth agenesis in humans and mice, which mainly involves the posterior teeth. To determine whether this gene is polymorphic in humans, we sequenced ≈2.1 kb of the entire four-exon region (exons 1, 2, 3 and 4; 1,026 bp) and exon-intron (1.1 kb) boundaries of 86 individuals sampled from Asian, European, and Native American populations. We provided evidence that humanPAX9polymorphisms are limited to exon 3 only and furnished details about the distribution of a mutation there in 350 Polish subjects. To investigate the pattern of selective pressure on exon 3, we sequenced ortholog regions of this exon in four species of New World monkeys and one gorilla. In addition, orthologous sequences ofPAX9available in public databases were also analyzed. Although several differences were identified between humans and other species, our findings support the view that strong purifying selection is acting onPAX9. New World and Old World primate lineages may, however, have different degrees of restriction for changes in this DNA region.
A base-excision DNA-repair protein finds intrahelical lesion bases by fast sliding in contact with DNA
Authors: Blainey Paul C. , van Oijen Antoine M. , Banerjee Anirban , Verdine Gregory L. , Xie X. Sunney
Published: April 2006

A central mystery in the function of site-specific DNA-binding proteins is the detailed mechanism for rapid location and binding of target sites in DNA. Human oxoguanine DNA glycosylase 1 (hOgg1), for example, must search out rare 8-oxoguanine lesions to prevent transversion mutations arising from oxidative stress. Here we report high-speed imaging of single hOgg1 enzyme molecules diffusing along DNA stretched by shear flow. Salt-concentration-dependent measurements reveal that such diffusion occurs as hOgg1 slides in persistent contact with DNA. At near-physiologic pH and salt concentration, hOgg1 has a subsecond DNA-binding time and slides with a diffusion constant as high as 5 × 10
6
bp
2
/s. Such a value approaches the theoretical upper limit for one-dimensional diffusion and indicates an activation barrier for sliding of only 0.5 kcal/mol (1 kcal = 4.2 kJ). This nearly barrierless Brownian sliding indicates that DNA glycosylases locate lesion bases by a massively redundant search in which the enzyme selectively binds 8-oxoguanine under kinetic control.
Dimerized
Drosophila
myosin VIIa: A processive motor
Authors: Yang Yi , Kovács Mihály , Sakamoto Takeshi , Zhang Fang , Kiehart Daniel P. , Sellers James R.
Published: April 2006

The molecular mechanism of processive movement of single myosin molecules from classes V and VI along their actin tracks has recently attracted extraordinary attention. Another member of the myosin superfamily, myosin VII, plays vital roles in the sensory function of
Drosophila
and mammals. We studied the molecular mechanism of
Drosophila
myosin VIIa, using transient kinetics and single-molecule motility assays. Myosin VIIa moves along actin filaments as a processive, double-headed single molecule when dimerized by the inclusion of a leucine zipper at the C terminus of the coiled-coil domain. Its motility is ≈8–10 times slower than that of myosin V, and its step size is 30 nm, which is consistent with the presence of five IQ motifs in its neck region. The kinetic basis for the processive motility of myosin VIIa is the relative magnitude of the release rate constants of phosphate (fast) and ADP (slow) as in myosins V and VI. The ATPase pathway is rate-limited by a reversible interconversion between two distinct ADP-bound actomyosin states, which results in high steady-state occupancy of a strongly actin-bound myosin species. The distinctive features of myosin VIIa (long run lengths, slow motility) will be very useful in video-based single-molecule applications. In cells, this kinetic behavior would allow myosin VIIa to exert and hold tension on actin filaments and, if dimerized, to function as a processive cargo transporter.
DNA strand breaks induced by near-zero-electronvolt electron attachment to pyrimidine nucleotides
Authors: Bao Xiaoguang , Wang Jing , Gu Jiande , Leszczynski Jerzy
Published: April 2006

To elucidate the mechanism of DNA strand breaks by low-energy electrons (LEE), theoretical investigations of the LEE attachment-induced C
5′

O
5′
σ bond breaking of pyrimidine nucleotides (5′-dCMPH and 5′-dTMPH) were performed by using the B3LYP/DZP++ approach. The results indicate that the pyrimidine nucleotides are able to capture electrons characterized by near-0-eV energy to form electronically stable radical anions in both the gas phase and aqueous solution. The mechanism of the LEE-induced single-strand bond breaking in DNA might involve the attachment of an electron to the bases of DNA and the formation of base-centered radical anions in the first step. Subsequently, these radical anions undergo either C

O or glycosidic bond breaking, yielding neutral ribose radical fragments and the corresponding phosphoric anions or base anions. The C

O bond cleavage is expected to dominate because of its low activation energy. In aqueous solutions, the significant increases in the electron affinities of pyrimidine nucleotides ensure the formation of electronically more stable radical anions of the nucleotides. The low activation energy barriers for the C
5′

O
5′
bond breaking predicted in this work are relevant when the counterions are close enough to the phosphate moiety of DNA.
Single-molecule kinetics reveals signatures of half-sites reactivity in dihydroorotate dehydrogenase A catalysis
Authors: Shi Jue , Dertouzos Joe , Gafni Ari , Steel Duncan , Palfey Bruce A.
Published: April 2006

Subunit activity and cooperativity of a homodimeric flavoenzyme, dihydroorotate dehydrogenase A (DHODA) from
Lactococcus lactis
, were characterized by employing single-molecule spectroscopy to follow the turnover kinetics of individual DHODA molecules, eliminating ensemble averaging. Because the enzyme-bound FMN is fluorescent in its oxidized state but not when reduced, a single DHODA molecule exhibits stepwise fluorescence changes during turnover, providing a signal to determine reaction kinetics and study cooperativity. Our results showed significant heterogeneity in the catalytic behaviors of individual dimer molecules, with only 40% interconverting between the three possible redox states: the fully fluorescent (both subunits oxidized), the half-fluorescent (one subunit oxidized and the other reduced), and the nonfluorescent (both subunits reduced). Forty percent of the single dimer traces showed turnovers between only the fully fluorescent and half-fluorescent states. The remaining 20% of the molecules interconverted only between the half-fluorescent state and the nonfluorescent state. Kinetic analysis revealed very similar reaction rates in both the reductive and oxidative half-reactions for different DHODA dimers. Our single-molecule data provide strong evidence for half-sites reactivity, in which only one subunit reacts at a time. The present study presents an effective way to explore the subunit catalytic activity and cooperativity of oligomeric enzymes by virtue of single-molecule fluorescence.
The expression level of the voltage-dependent anion channel controls life and death of the cell
Authors: Abu-Hamad Salah , Sivan Sara , Shoshan-Barmatz Varda
Published: April 2006

Mitochondria not only generate cellular energy, but also act as the point for cellular decisions leading to apoptosis. The voltage-dependent anion channel (VDAC), as a major mitochondrial outer-membrane transporter, has an important role in energy production by controlling metabolite traffic and is also recognized as a key protein in mitochondria-mediated apoptosis. In this study, the role of VDAC1 in regulating cell survival and death was investigated by silencing endogenous human (h)VDAC1 expression by using a short hairpin RNA (shRNA)-expressing vector. The shRNA effectively down-regulated the expression in human T-REx-293 cells of hVDAC1 but not murine (m)VDAC1. Cells in which hVDAC1 expression was decreased by ≈90% proliferated extremely slowly. Normal growth was, however, restored upon expression of mVDAC1 in a tetracycline-regulated manner. Although low tetracycline concentrations promoted cell growth, high concentrations induced mVDAC1 overexpression, leading to cell death. Cells with low levels of VDAC1 showed 4-fold-lower ATP-synthesis capacity and contained low ATP and ADP levels, with a strong correlation between ATP levels and cell growth, suggesting limited metabolite exchange between mitochondria and cytosol. The possibility of suppressing endogenous hVDAC1 expression and introducing native and mutated mVDAC1 is used to further explore the involvement of VDAC1 in apoptosis. Cells suppressed for hVDAC1 but expressing either native mVDAC1 or an E72Q mutant underwent apoptosis induced by various stimuli that can be inhibited by ruthenium red in the native cells but not in the mutated cells, suggesting that VDAC1 regulates apoptosis independent of the apoptosis-inducing pathway.
Identification of genes subject to positive selection in uropathogenic strains of
Escherichia coli
: A comparative genomics approach
Authors: Chen Swaine L. , Hung Chia-Seui , Xu Jian , Reigstad Christopher S. , Magrini Vincent , Sabo Aniko , Blasiar Darin , Bieri Tamberlyn , Meyer Rekha R. , Ozersky Philip , Armstrong Jon R. , Fulton Robert S. , Latreille J. Phillip , Spieth John , Hooton Thomas M. , Mardis Elaine R. , Hultgren Scott J. , Gordon Jeffrey I.
Published: April 2006

Escherichia coli
is a model laboratory bacterium, a species that is widely distributed in the environment, as well as a mutualist and pathogen in its human hosts. As such,
E. coli
represents an attractive organism to study how environment impacts microbial genome structure and function. Uropathogenic
E. coli
(UPEC) must adapt to life in several microbial communities in the human body, and has a complex life cycle in the bladder when it causes acute or recurrent urinary tract infection (UTI). Several studies designed to identify virulence factors have focused on genes that are uniquely represented in UPEC strains, whereas the role of genes that are common to all
E. coli
has received much less attention. Here we describe the complete 5,065,741-bp genome sequence of a UPEC strain recovered from a patient with an acute bladder infection and compare it with six other finished
E. coli
genome sequences. We searched 3,470 ortholog sets for genes that are under positive selection only in UPEC strains. Our maximum likelihood-based analysis yielded 29 genes involved in various aspects of cell surface structure, DNA metabolism, nutrient acquisition, and UTI. These results were validated by resequencing a subset of the 29 genes in a panel of 50 urinary, periurethral, and rectal
E. coli
isolates from patients with UTI. These studies outline a computational approach that may be broadly applicable for studying strain-specific adaptation and pathogenesis in other bacteria.
Determinants of specific RNA interference-mediated silencing of human β-globin alleles differing by a single nucleotide polymorphism
Authors: Dykxhoorn Derek M. , Schlehuber Lisa D. , London Irving M. , Lieberman Judy
Published: April 2006

A single nucleotide polymorphism (SNP) in the sickle β-globin gene (β
S
) leads to sickle cell anemia. Sickling increases sharply with deoxy sickle Hb concentration and decreases with increasing fetal γ-globin concentration. Measures that decrease sickle Hb concentration should have an antisickling effect. RNA interference (RNAi) uses small interfering (si)RNAs for sequence-specific gene silencing. A β
S
siRNA with position 10 of the guide strand designed to align with the targeted β

S

SNP specifically silences β

S

gene expression without affecting the expression of the γ-globin or normal β-globin (β

A

) genes. Silencing is increased by altering the 5′ end of the siRNA antisense (guide) strand to enhance its binding to the RNA-induced silencing complex (RISC). Specific β
S
silencing was demonstrated by using a luciferase reporter and full-length β
S
cDNA transfected into HeLa cells and mouse erythroleukemia cells, where it was expressed in the context of the endogenous β-globin gene promoter and the locus control region enhancers. When this strategy was used to target β

E

, silencing was not limited to the mutant gene but also targeted the normal β

A

gene. siRNAs, mismatched with their target at position 10, guided mRNA cleavage in all cases except when two bulky purines were aligned. The specific silencing of the β

S

-globin gene, as compared with β

E

, as well as studies of silencing SNP mutants in other diseases, indicates that siRNAs developed to target a disease-causing SNP will be specific if the mutant residue is a pyrimidine and the normal residue is a purine.
Regulatory CD56brightnatural killer cells mediate immunomodulatory effects of IL-2Rα-targeted therapy (daclizumab) in multiple sclerosis
Authors: Bielekova Bibiana , Catalfamo Marta , Reichert-Scrivner Susan , Packer Amy , Cerna Magdalena , Waldmann Thomas A. , McFarland Henry , Henkart Pierre A. , Martin Roland
Published: April 2006

Administration of daclizumab, a humanized mAb directed against the IL-2Rα chain, strongly reduces brain inflammation in multiple sclerosis patients. Here we show that daclizumab treatment leads to only a mild functional blockade of CD4+T cells, the major candidate in multiple sclerosis pathogenesis. Instead, daclizumab therapy was associated with a gradual decline in circulating CD4+and CD8+T cells and significant expansion of CD56brightnatural killer (NK) cellsin vivo, and this effect correlated highly with the treatment response.In vitrostudies showed that NK cells inhibited T cell survival in activated peripheral blood mononuclear cell cultures by a contact-dependent mechanism. Positive correlations between expansion of CD56brightNK cells and contraction of CD4+and CD8+T cell numbers in individual patientsin vivoprovides supporting evidence for NK cell-mediated negative immunoregulation of activated T cells during daclizumab therapy. Our data support the existence of an immunoregulatory pathway wherein activated CD56brightNK cells inhibit T cell survival. This immunoregulation has potential importance for the treatment of autoimmune diseases and transplant rejection and toward modification of tumor immunity.
In a bovine model of onchocerciasis, protective immunity exists naturally, is absent in drug-cured hosts, and is induced by vaccination
Authors: Tchakouté Virginia L. , Graham Simon P. , Jensen Siv Aina , Makepeace Benjamin L. , Nfon Charles K. , Njongmeta Leo M. , Lustigman Sara , Enyong Peter A. , Tanya Vincent N. , Bianco Albert E. , Trees Alexander J.
Published: April 2006

Onchocerciasis (river blindness) is a major parasitic disease of humans in sub-Saharan Africa caused by the microfilarial stage of the nematodeOnchocerca volvulus. UsingOnchocerca ochengi, a closely related species which infects cattle and is transmitted by the same black fly vector (Simulium damnosum sensu lato) asO. volvulus, we have conducted longitudinal studies after either natural field exposure or experimental infection to determine whether, and under what circumstances, protective immunity exists in onchocerciasis. On the basis of the adult worm burdens (nodules) observed, we determined that cattle reared in endemic areas without detectable parasites (putatively immune) were significantly less susceptible to heavy field challenge than age-matched, naïve controls (P= 0.002), whereas patently infected cattle, cured of infection by adulticide treatment with melarsomine, were fully susceptible. Cattle immunized with irradiated third-stage larvae were significantly protected against experimental challenge (100% reduction in median nodule load,P= 0.003), and vaccination also conferred resistance to severe and prolonged field challenge (64% reduction in median nodule load,P= 0.053; and a significant reduction in microfilarial positivity rates and density,P< 0.05). These results constitute evidence of protective immunity in a naturally evolved host–Onchocercasp. relationship and provide proof-of-principle for immunoprophylaxis under experimental and field conditions.
Viral and therapeutic control of IFN-β promoter stimulator 1 during hepatitis C virus infection
Authors: Loo Yueh-Ming , Owen David M. , Li Kui , Erickson Andrea K. , Johnson Cynthia L. , Fish Penny M. , Carney D. Spencer , Wang Ting , Ishida Hisashi , Yoneyama Mitsutoshi , Fujita Takashi , Saito Takeshi , Lee William M. , Hagedorn Curt H. , Lau Daryl T.-Y. , Weinman Steven A. , Lemon Stanley M. , Gale Michael
Published: April 2006

Viral signaling through retinoic acid-inducible gene-I (RIG-I) and its adaptor protein, IFN promoter-stimulator 1 (IPS-1), activates IFN regulatory factor-3 (IRF-3) and the host IFN-α/β response that limits virus infection. The hepatitis C virus (HCV) NS3/4A protease cleaves IPS-1 to block RIG-I signaling, but how this regulation controls the host response to HCV is not known. Moreover, endogenous IPS-1 cleavage has not been demonstrated in the context of HCV infection
in vitro
or
in vivo
. Here, we show that HCV infection transiently induces RIG-I- and IPS-1-dependent IRF-3 activation. This host response limits HCV production and constrains cellular permissiveness to infection. However, HCV disrupts this response early in infection by NS3/4A cleavage of IPS-1 at C508, releasing IPS-1 from the mitochondrial membrane. Cleavage results in subcellular redistribution of IPS-1 and loss of interaction with RIG-I, thereby preventing downstream activation of IRF-3 and IFN-β induction. Liver tissues from chronically infected patients similarly demonstrate subcellular redistribution of IPS-1 in infected hepatocytes and IPS-1 cleavage associated with a lack of ISG15 expression and conjugation of target proteins
in vivo
. Importantly, small-molecule inhibitors of NS3/4A prevent cleavage and restore RIG-I signaling of IFN-β induction. Our results suggest a dynamic model in which early activation of IRF-3 and induction of antiviral genes are reversed by IPS-1 proteolysis and abrogation of RIG-I signaling as NS3/4A accumulates in newly infected cells. HCV protease inhibitors effectively prevent IPS-1 proteolysis, suggesting they may be capable of restoring this innate host response in clinical practice.
Adhesion of single bacterial cells in the micronewton range
Authors: Tsang Peter H. , Li Guanglai , Brun Yves V. , Freund L. Ben , Tang Jay X.
Published: April 2006

The adhesion of bacteria to surfaces plays critical roles in the environment, disease, and industry. In aquatic environments,
Caulobacter crescentus
is one of the first colonizers of submerged surfaces. Using a micromanipulation technique, we measured the adhesion force of single
C. crescentus
cells attached to borosilicate substrates through their adhesive holdfast. The detachment forces measured for 14 cells ranged over 0.11 to 2.26 μN, averaging 0.59 ± 0.62 μN. Based on the calculation of stress distribution with the finite element analysis method (dividing an object into small grids and calculating relevant parameters for all of the elements), the adhesion strength between the holdfast and the substrate is >68 N/mm
2
in the central region of contact. To our knowledge, this strength of adhesion is the strongest ever measured for biological adhesives.
Dual Diagnosis—Policy and Practice in Italy
Authors: Carrà Giuseppe , Clerici Clerici
Published: April 2006

In Italy, dual diagnosis issues are affected by distinctive historical pathways. Since the end of the 1970s, the addiction field has been starved of psychiatric contribution, with the emphasis being on a pedagogical model of substance‐related disorders and a bio‐psycho‐social model for mental health. As such, dual diagnosis treatment, service models, and research have only been developed in the last fifteen years. Substantial training needs with regard to dual diagnosis are identified in addiction and mental health professionals, and new graduate and undergraduate programs are required. Further research is needed as well as an evidence‐based health policy from national and regional government.
Validity of the Distinction Between Primary and Secondary Substance Use Disorder in Patients with Bipolar Disorder: Data from the First 1000 STEP‐BD Participants
Authors: Fossey Mark D. , Otto Michael W. , Yates William R. , Wisniewski Steve R. , Gyulai Gyulai , Allen Michael H. , Miklowitz David J. , Coon Kim A. , Ostacher Michael J. , Neel Jackie L. , Thase Michael E. , Sachs Gary S. , Weiss Roger D. ,   for STEP‐BD Investigators
Published: April 2006

The validity of a primary / secondary substance use disorder (SUD) distinction was evaluated in the first 1000 patients enrolled in the Systematic Treatment Enhancement Program for Bipolar Disorder. Patients with primary SUD (n = 116) were compared with those with secondary SUD (n = 275) on clinical course variables. Patients with secondary SUD had fewer days of euthymia, more episodes of mania and depression, and a greater history of suicide attempts. These findings were fully explained by variations in age of onset of bipolar disorder. The order of onset of SUDs was not linked to bipolar outcomes when age of onset of bipolar disorder was statistically controlled. The primary/secondary distinction for SUD is not valid when variations in the age of onset of the non‐SUD are linked to course characteristics.
Differing Effects of Antipsychotic Medications on Substance Abuse Treatment Patients with Co‐occurring Psychotic and Substance Abuse Disorders
Authors: Stuyt Elizabeth B. , Sajbel Terrie A. , Allen Michael H.
Published: April 2006

This retrospective study of patients treated in a ninety‐day, inpatient, dual‐diagnosis treatment program examined antipsychotic effectiveness in this population using length of stay in treatment and successful program completion as outcome measures. All patients with co‐occurring substance dependence and schizophrenia or schizoaffective disorder treated with olanzapine, risperidone, ziprasidone, and typical depot neuroleptics from January 2001 to December 2003 (n = 55) are the subjects of this study. Patients stayed longer in treatment when taking risperidone (82 ± 19 days) or ziprasidone (74 ± 21 days) compared with olanzapine (44 ± 30 days) or typicals (47 ± 36 days). Eighty‐eight percent of risperidone patients and 64% of ziprasidone patients successfully completed the program, while only 33% of olanzapine patients and 40% of patients on typicals successfully completed the program. Risperidone and ziprasidone were associated with significantly better program performance than olanzapine or depot typicals in this population. Possible reasons for this difference are discussed.
Problem Drinking in Women Evaluated for Infertility
Authors: Chang Chang , McNamara Tay K. , Haimovici Haimovici , Hornstein Mark D.
Published: April 2006

Clinicians may wish to use the T‐ACE, a screening instrument for prenatal risk drinking, for their infertile patients. Twenty‐eight T‐ACE negative and 23 T‐ACE positive women presenting to an academic infertility clinic completed two interviews about their drinking. The 23 T‐ACE positive participants were also randomized to receive a brief intervention. The T‐ACE distinguished between heavier and lighter patterns of alcohol use in this sample. Moreover, it appeared that although the average quantity of alcohol consumed per drinking day was unchanged, the overall mean percentage of days drinking declined significantly from the time of enrollment to follow‐up in all groups.
Modeling Aggregate Exposures to Glycol Ethers from Use of Commercial Floor Products
Authors: Koontz Michael , Price Paul , Hamilton John , Daggett Daniel , Sielken Robert , Bretzlaff Robert , Tyler Tipton
Published: April 2006

Computer modeling of aggregate exposure provides the capability to estimate the range of doses that can occur from product use and to understand the relative importance of different routes of exposure. This paper presents an assessment of aggregate occupational exposure to two glycol ethers used as solvents in floor maintenance products for industrial and institutional facilities, using a simulation tool named PROMISE. Three commercial floor-care products were assumed to be applied in sequence—a floor stripper, then a floor cleaner, and lastly a protective coating. The glycol ethers modeled were ethylene glycol butyl ether (EGBE) in the floor stripper and in the floor cleaner, and dipropylene glycol methyl ether (DPGME) in the coating. Modeling uncertainty was assessed through a comparison of the PROMISE inhalation exposure estimates with those from an independent model (MCCEM), and parameter uncertainty was investigated using PROMISE software’s Monte Carlo simulation capabilities. Modeling results indicated that inhalation is the dominant exposure route. The predicted average air concentration and inhalation dose from PROMISE agreed with the second model (MCCEM) within 10%. Monte Carlo simulation indicated that the upper end of the aggregate-dose distribution for the scenario was more than 50% higher than the value of the point estimate. The modeled 8-h TWA concentrations for EGBE and DPGME were lower than the corresponding permissible exposure limits American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) by at least a factor of 20, indicating that under the assumed conditions work-place exposures to glycol ethers are below levels of concern.
Safety Assessment of 4′-Thio-β-d-Arabinofuranosylcytosine in the Beagle Dog Suggests a Drug-Induced Centrally Mediated Effect on the Hypothalamic-Pituitary-Adrenal Axis
Authors: Colagiovanni Dorothy B. , Drolet Daniel W. , Dihel Larry , Meyer Dennis J. , Hart Karen , Wolf Julie
Published: April 2006

4′-Thio- β-d-arabinofuranosylcytosine (OSI-7836) is a nucleoside analogue with structural similarity to gemcitabine and cytarabine (ara-C). Myelosuppression, reversible transaminase elevations, and flu-like symptoms are common side effects associated with human use of gemcitabine and ara-C. Fatigue is also associated with the use of gemcitabine and OSI-7836 in humans. To better understand the toxicity of OSI-7836, subchronic studies were conducted in dogs. OSI-7836 was administered on days 1 and 8 or on days 1, 2, and 3 of a 21-day dose regimen. These schedules attempted to match clinical trial dosing regimens. Routine toxicity study end points demonstrated that OSI-7836 was primarily cytotoxic to the gastrointestinal tract, bone marrow, and testes; the myelotoxicity was mild and reversible. Plasma pharmacokinetics were dose-linear with an elimination half-life of 2.2 h. Follow-up single dose experiments in dogs assessed drug effects on lymphocyte subpopulations and on adrenal and thyroid function. Populations of T and B cells were equally reduced following OSI-7836 administration. There were no adverse effects on thyroid function, but there were marked reductions in circulating cortisol and adrenocorticotropic hormone concentrations suggesting a centrally mediated impairment of the hypothalamic-pituitary-adrenal axis. These findings show a toxicological profile with OSI-7836 similar to other nucleoside analogues and suggest that the beagle is a model for studying one possible cause of OSI-7836-related fatigue, impaired function of the hypothalamic-pituitary-adrenal axis.
BBS: An Energy Efficient Localized Routing Scheme for Query Processing in Wireless Sensor Networks
Authors: Lian Jie , Naik Kshirasagar , Agnew Gordon B. , Chen Lei , Özsu M. Tamer
Published: April 2006

A wireless sensor network (WSNET) can support various types of queries. The energy resource of sensors constrains the total number of query responses, called query capacity, received by the sink. There are four problems in the existing approaches for energy-efficient query processing in WSNETs: the fact that sensors near the sink drain their energy much faster than distant sensors has been overlooked, routing trees (RT) are rooted at the sink, and therefore, aggregative queries are less energy-efficient, data reception cost has been ignored, and flooding is used in query distribution or RT construction.

In this paper, we propose a Broadcasting-Based query Scheme (BBS) to address the above problems. BBS reduces the energy depletion rate of sensors near the sink, builds different localized RTs for different query types, and eliminates the flooding cost of query distribution. Compared to the existing approaches, simulation studies show that BBS produces significant improvement in the query capacity for non-holistic queries (10%—100% capacity improvement) and holistic queries (up to an order of magnitude of capacity improvement).
MicroRouting: A Scalable and Robust Communication Paradigm for Sparse Ad Hoc Networks
Authors: Das Saumitra M. , Pucha Himabindu , Hu Y. Charlie
Published: April 2006

Mobile ad hoc networks are self-organizing networks that provide rapid network connectivity in infrastructureless environments. Most routing protocols designed for MANETs assume connected networks. Such a restriction directly limits the application domains of MANETs. In this paper, we study the problem of providing time-critical data delivery in sparse ad hoc networks where network partition can last for a long period, without imposing any restrictions on the node mobility. Supporting real-time communication with unconstrained mobility is important to many mission-critical applications such as battlefields and search and rescue in large-scale disaster areas.

In this paper, we propose microrouting networks consisting of tiny nodes similar to sensors but without transducers (called microrouters) as a substrate for time-critical data delivery in sparse MANETs. We describe the microrouting protocol for the resulting hybrid network which exploits the fact that microrouters are stationary, but are constrained by energy and memory. Key features of the microrouting protocol design include stateless architecture and localized route repair. We demonstrate the viability of the microrouting network architecture via detailed simulation evaluation. Our results show that microrouting networks running the microrouting protocol efficiently extend the connectivity of sparse MANETs and provide high packet delivery ratios.
Do multidimensional intrinsic and extrinsic motivation profiles discriminate between athlete scholarship status and gender?
Authors: Kingston Kieran M. , Horrocks Chris S. , Hanton Sheldon
Published: April 2006

The purpose of this investigation was to examine whether levels of multidimensional intrinsic, multidimensional extrinsic motivation and amotivation could accurately discriminate scholarship status and gender in United States collegiate athletes. Participants comprised 82 male (M age = 19.89, SD=1.39) and 90 female (M age = 20.26, SD=1.63) collegiate athletes. Each participant completed a demographic questionnaire and the Sports Motivation Scale (Pelletier, L.G., Fortier, M.S., Vallerand, R.J., Tuson, K. M., Brière, N.M., & Blais, M.R. (1995). Toward a new measure of intrinsic motivation, extrinsic motivation, and amotivation in sports: The Sports Motivation Scale. Journal of Sport & Exercise Psychology, 17, 35–53). Two‐group discriminant analysis revealed a significant canonical function correctly classifying 72.8% of the cases into either the scholarship or non‐scholarship group. The least self‐determined forms of extrinsic motivation were the strongest contributors to this discrimination. With respect to gender, a significant discriminant function existed, again with the least self‐determined forms of extrinsic motivation representing the strongest discriminating variables. The results provide converging evidence that rewards such as scholarships can undermine intrinsic motivation. Further, as well as being consistent with theoretical predictions embedded in cognitive evaluation theory, the results of this study suggest that in addition to undermining intrinsic motivation, scholarships could foster non‐self‐determined forms of motivation.
Multivariate isokinetic asymmetry of the knee and shoulder in elite volleyball players
Authors: Markou S. , Vagenas G.
Published: April 2006

Muscle strength asymmetries have been investigated in athletes under the assumption of their connection to functional discrepancies and injuries. In volleyball, which is a highly asymmetric sport, this assumption becomes a well established research hypothesis. Given the almost complete lack of scientific evidence on this hypothesis, the present study focused on the detailed multivariate quantification of muscle asymmetries in offensive volleyball players. Twenty‐four elite athletes (age 24.71±4.44 years, weight 84.62±6.24, height 190.08±5.58) were tested for concentric isokinetic muscle strength (a) of the internal and external rotators of the shoulder and (b) of the quadriceps and hamstrings of the knee at 60o/s. Significant multivariate results were found for absolute (Max‐Min) asymmetry in the upper (Hotteling's T 2=8.801, F=7.447, P=0.001) and the lower limbs (Hotteling's T 2=16.382, F=13.862, P=0.000), for fluctuating asymmetry (Dominant‐Non Dominant) in the upper limbs (Hotteling's T 2=5.584, F=4.296, P=0.013) and for directional asymmetry (Left‐Right) in the lower limbs (Hotteling's T 2=3.593, F=3.041, P=0.036). It appears that the upper and lower limbs of offensive volleyball players present significant composite muscle strength asymmetries, which should be taken into consideration in training and rehabilitation.
ECSS position statement: Exercise and obesity
Authors: Fogelholm Mikael , Stallknecht Bente , Van Baak Marleen
Published: April 2006

This is a review on the effects of physical exercise on weight, body composition and health in prevention and management of obesity. Individuals who maintain or increase their physical activity also show the best weight control over a period of several years. However, physical activity at baseline of prospective studies does not consistently predict weight change, perhaps because of changes in physical activity during the follow‐up. Moderate‐intensity (e.g. walking) physical activity during dietinduced weight reduction leads to modest improvements in weight, abdominal fat and total fat loss. Moderate exercise 250–300 min/wk is recommended for weight reducing purposes. For maintenance of reduced body weight, more than 60 min moderate exercise per day after weight reduction might be needed. Studies have found a more pronounced training‐induced loss of visceral compared to subcutaneous fat in overweight and obese subjects. Physical activity will help to lower risk of insulin resistance, type 2 diabetes, dyslipidemia, hypertension and the metabolic syndrome in overweight and obese individuals and that more pronounced effects can be attained in combination with maintained weight loss. The intensity of physical activity should be at least moderate (>30–40% VO2max) to cause metabolic health benefits. A suitable frequency for moderate‐intensity physical activity seems to be daily, and for vigorous activity every other day.
RGMa inhibition promotes axonal growth and recovery after spinal cord injury
Authors: Hata Katsuhiko , Fujitani Masashi , Yasuda Yuichi , Doya Hideo , Saito Tomoko , Yamagishi Satoru , Mueller Bernhard K. , Yamashita Toshihide
Published: April 2006

Repulsive guidance molecule (RGM) is a protein implicated in both axonal guidance and neural tube closure. We report RGMa as a potent inhibitor of axon regeneration in the adult central nervous system (CNS). RGMa inhibits mammalian CNS neurite outgrowth by a mechanism dependent on the activation of the RhoA–Rho kinase pathway. RGMa expression is observed in oligodendrocytes, myelinated fibers, and neurons of the adult rat spinal cord and is induced around the injury site after spinal cord injury. We developed an antibody to RGMa that efficiently blocks the effect of RGMa in vitro. Intrathecal administration of the antibody to rats with thoracic spinal cord hemisection results in significant axonal growth of the corticospinal tract and improves functional recovery. Thus, RGMa plays an important role in limiting axonal regeneration after CNS injury and the RGMa antibody offers a possible therapeutic agent in clinical conditions characterized by a failure of CNS regeneration.
Retention of function without normal disc morphogenesis occurs in cone but not rod photoreceptors
Authors: Farjo Rafal , Skaggs Jeff S. , Nagel Barbara A. , Quiambao Alexander B. , Nash Zack A. , Fliesler Steven J. , Naash Muna I.
Published: April 2006

It is commonly assumed that photoreceptor (PR) outer segment (OS) morphogenesis is reliant upon the presence of peripherin/rds, hereafter termed Rds. In this study, we demonstrate a differential requirement of Rds during rod and cone OS morphogenesis. In the absence of this PR-specific protein, rods do not form OSs and enter apoptosis, whereas cone PRs develop atypical OSs and are viable. Such OSs consist of dysmorphic membranous structures devoid of lamellae. These tubular OSs lack any stacked lamellae and have reduced phototransduction efficiency. The loss of Rds only appears to affect the shape of the OS, as the inner segment and connecting cilium remain intact. Furthermore, these structures fail to associate with the specialized extracellular matrix that surrounds cones, suggesting that Rds itself or normal OS formation is required for this interaction. This study provides novel insight into the distinct role of Rds in the OS development of rods and cones.
Nonvesicular sterol movement from plasma membrane to ER requires oxysterol-binding protein–related proteins and phosphoinositides
Authors: Raychaudhuri Sumana , Im Young Jun , Hurley James H. , Prinz William A.
Published: April 2006

Sterols are moved between cellular membranes by nonvesicular pathways whose functions are poorly understood. In yeast, one such pathway transfers sterols from the plasma membrane (PM) to the endoplasmic reticulum (ER). We show that this transport requires oxysterol-binding protein (OSBP)–related proteins (ORPs), which are a large family of conserved lipid-binding proteins. We demonstrate that a representative member of this family, Osh4p/Kes1p, specifically facilitates the nonvesicular transfer of cholesterol and ergosterol between membranes in vitro. In addition, Osh4p transfers sterols more rapidly between membranes containing phosphoinositides (PIPs), suggesting that PIPs regulate sterol transport by ORPs. We confirmed this by showing that PM to ER sterol transport slows dramatically in mutants with conditional defects in PIP biosynthesis. Our findings argue that ORPs move sterols among cellular compartments and that sterol transport and intracellular distribution are regulated by PIPs.
A specialized processing body that is temporally and asymmetrically regulated during the cell cycle in Saccharomyces cerevisiae
Authors: Gill Tina , Aulds Jason , Schmitt Mark E.
Published: April 2006

RNase mitochondrial RNA processing (MRP) is an essential ribonucleoprotein endoribonuclease that functions in the degradation of specific mRNAs involved in cell cycle regulation. We have investigated where this processing event occurs and how it is regulated. As expected, results demonstrate that RNase MRP is predominantly localized in the nucleolus, where it processes ribosomal RNAs. However, after the initiation of mitosis, RNase MRP localizes throughout the entire nucleus and in a single discrete cytoplasmic spot that persists until the completion of telophase. Furthermore, this spot was asymmetrically found in daughter cells, where the RNase MRP substrate, CLB2 mRNA, localizes. Both the mitotic exit network and fourteen early anaphase release pathways are nonessential but important for the temporal changes in localization. Asymmetric localization was found to be dependent on the locasome. The evidence suggests that these spots are specialized processing bodies for the degradation of transcripts that are cell cycle regulated and daughter cell localized. We have called these TAM bodies for temporal asymmetric MRP bodies.
Endogenous IRBP can be dispensable for generation of natural CD4+CD25+ regulatory T cells that protect from IRBP-induced retinal autoimmunity
Authors: Grajewski Rafael S. , Silver Phyllis B. , Agarwal Rajeev K. , Su Shao-Bo , Chan Chi-Chao , Liou Gregory I. , Caspi Rachel R.
Published: April 2006

Susceptibility to experimental autoimmune uveitis (EAU), a model for human uveitis induced in mice with the retinal antigen interphotoreceptor retinoid-binding protein (IRBP), is controlled by “natural” CD4+CD25+ regulatory T (T reg) cells. To examine whether endogenous expression of IRBP is necessary to generate these T reg cells, we studied responses of IRBP knockout (KO) versus wild-type (WT) mice. Unexpectedly, not only WT but also IRBP KO mice immunized with a uveitogenic regimen of IRBP in complete Freund's adjuvant (CFA) exhibited CD25+ regulatory cells that could be depleted by PC61 treatment, which suppressed development of uveitogenic effector T cells and decreased immunological responses to IRBP. These EAU-relevant T reg cells were not IRBP specific, as their activity was not present in IRBP KO mice immunized with IRBP in incomplete Freund's adjuvant (IFA), lacking mycobacteria (whereas the same mice exhibited normal T reg cell activity to retinal arrestin in IFA). We propose that mycobacterial components in CFA activate T reg cells of other specificities to inhibit generation of IRBP-specific effector T cells in a bystander fashion, indicating that effective T reg cells can be antigen nonspecific. Our data also provide the first evidence that generation of specific T reg cells to a native autoantigen in a mouse with a diverse T cell repertoire requires a cognate interaction.
Dystroglycan is selectively cleaved at the parenchymal basement membrane at sites of leukocyte extravasation in experimental autoimmune encephalomyelitis
Authors: Agrawal Smriti , Anderson Per , Durbeej Madeleine , van Rooijen Nico , Ivars Fredrik , Opdenakker Ghislain , Sorokin Lydia M.
Published: April 2006

The endothelial cell monolayer of cerebral vessels and its basement membrane (BM) are ensheathed by the astrocyte endfeet, the leptomeningeal cells, and their associated parenchymal BM, all of which contribute to establishment of the blood–brain barrier (BBB). As a consequence of this unique structure, leukocyte penetration of cerebral vessels is a multistep event. In mouse experimental autoimmune encephalomyelitis (EAE), a widely used central nervous system inflammatory model, leukocytes first penetrate the endothelial cell monolayer and underlying BM using integrin β1-mediated processes, but mechanisms used to penetrate the second barrier defined by the parenchymal BM and glia limitans remain uninvestigated. We show here that macrophage-derived gelatinase (matrix metalloproteinase [MMP]-2 and MMP-9) activity is crucial for leukocyte penetration of the parenchymal BM. Dystroglycan, a transmembrane receptor that anchors astrocyte endfeet to the parenchymal BM via high affinity interactions with laminins 1 and 2, perlecan and agrin, is identified as a specific substrate of MMP-2 and MMP-9. Ablation of both MMP-2 and MMP-9 in double knockout mice confers resistance to EAE by inhibiting dystroglycan cleavage and preventing leukocyte infiltration. This is the first description of selective in situ proteolytic damage of a BBB-specific molecule at sites of leukocyte infiltration.