bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic modelling for cutting with serrated end mills – a parametric representation approach
Authors: Hosseini A , Moetakef-Imani B , Kishawy H A
Published: June 2011

Rough end mills with a serrated profile along the cutting edge are broadly used for suppressing chatter vibrations encountered during machining. The serrated profile of the cutting edge has a phase shift from one flute to the next and interferes with the regeneration of waviness of the cut surface. The edge serration alters periodically along the axial direction and therefore calculation of chip load for serrated tools is different from that of traditional tools. In the present paper, serrated cutting edges are analytically defined and geometrically modelled as a B-spline curve. The chip load along the serrated cutting edge is computed by a newly proposed universal algorithm. The presented algorithm computes the instantaneous chip load for any geometry including straight, helical, and serrated. The validity of the presented model is investigated geometrically using solid modelling techniques. In addition to geometrical model verification, milling tests for regular, serrated cylindrical, and serrated tapered ball end mills were conducted to validate the model's accuracy. The simulation results confirmed that the presented model can calculate the chip load with high accuracy and can be implemented effectively for force simulations of serrated cutters.
Investigation of recast layers generated by a powder-mixed dielectric micro electrical discharge machining process
Authors: Tan P C , Yeo S H
Published: June 2011

The use of powder-mixed dielectrics in micro-electrical discharge machining (micro-EDM) is an important technological development with the potential to improve machined surface quality and impart functional properties to machined surfaces. These process capabilities are vital in the manufacture of microcomponents since enhancing machined surface characteristics can extend their service life and improve their functionality. While studies have been conducted on gap enlargement and surface roughness, there is limited work on subsurface characteristics. The present study assessed the recast layer thickness, given the potential of applying powder-mixed dielectrics to recast layer reduction and surface modification. Moreover, its process characteristics under specific micro-EDM process parameters, such as low powder concentrations, nano-sized powder granularities, and sub-microsecond pulse-on time durations, which have received limited coverage, have been elucidated. The study has revealed evident changes in recast layer thickness under different machining conditions. The reductions in recast layer thickness at a powder concentration of 0.1 g/l were found to range between 15 per cent and 35 per cent for pulse-on time durations between 166 ns and 606 ns. Furthermore, flushing effects from tool electrode rotation have been shown to exert an influence on recast layer thickness as well as on the amount of powder particles within the discharge gap.
Optical investigations of the early combustion phase in spark ignition boosted engines
Authors: Tornatore C , Sementa P , Merola S S
Published: June 2011

An improved understanding of the thermo-fluid dynamic phenomena that occur during the combustion process in boosted spark ignition engines is necessary for future developments in these engines. In particular, increased understanding of flame kernel evolution is fundamental since the initial growth of the flame contributes significantly to cycle-to-cycle variation in engine performance and emissions. In this work, flame inception and early stages of the combustion process were investigated in an optically accessible single-cylinder ported fuel injection engine. This engine was equipped with the cylinder head of new generation spark ignition turbocharged engine with the same characteristics as the research engine. Cycle-resolved visualization was applied to follow the flame propagation from the spark ignition to the flame kernel growth. A retrieval procedure for the optical data was realized to obtain information about the flame radius evolution. Natural emission spectroscopy in the ultraviolet–visible wavelength range allowed the detection of the chemical markers of the combustion process such as CH, OH, and HCO radicals, and formaldehyde molecules.

In-cylinder optical investigations were correlated with engine parameter measurements obtained by conventional methods.
Fuzzy sliding mode control based on hybrid Taguchi genetic algorithm for magneto-rheological suspension system
Authors: Dong X-M , Yu M , Liao C-R
Published: June 2011

Magneto-rheological (MR) suspension systems display non-linearity and parameter uncertainty and thus it is difficult to derive an accurate model for designing a model-based controller. In this study, a novel fuzzy sliding mode control (FSMC) approach based on the hybrid Taguchi genetic algorithm (HTGA) is proposed to suppress the vibration of the MR suspension system. As the first step, the MR absorber is designed and manufactured based on the damping force level and mechanical dimensions required for the test car. After experimentally measuring the current-dependent damping force characteristic, a precise inverse model of the MR absorber is formulated. Subsequently, FSMC based on the HTGA is formulated on the basis of a quarter car model incorporated with an MR absorber. The linguistic variables and control rules of the fuzzy logic controller are optimized using the HTGA. For comparison purposes, two representative controllers including a conventional sliding mode controller and a fuzzy logic controller are also proposed. Finally, simulations and a road test are performed to validate the effectiveness and robustness of the proposed FSMC.
Memory Impairment and Executive Dysfunction are Associated with Inadequately Controlled Diabetes in Older Adults
Authors: Grober Ellen , Hall Charles B. , Hahn Steven R. , Lipton Richard B.
Published: June 2011

Objective: To assess the cross-sectional relationship of glycemic control to memory impairment and executive dysfunction in older adults with diabetes treated at an urban primary care center. Participants and Methods: As part of a primary care-based cognitive screening program, we identified adults age 65 or older with a diagnosis of diabetes. Glycosylated hemoglobin level (HbA1c) was used to define diabetes as controlled (HbA1c <7) or inadequately controlled(HbA1c ≥ 7). Episodic memory was measured by quartile of free recall scores on the Free and Cued Selective Reminding Test. Executive function was measured using an ordinal composite score derived from animal fluency and months backward. These were the main predictors of diabetic control. Results: The 169 participants with diabetes had a median age of 74. The sample was 38% African American and 42% Latino. One hundred four (61%) had inadequately controlled diabetes. Memory impairment and executive dysfunction were independent predictors of diabetic control after adjusting for age and education. Binary logistic regression models indicated that the odds of inadequately controlled diabetes was higher for patients in the worst quartile of memory functioning compared to patients in higher quartiles of memory functioning (odds ratio = 6.4; 95% confidence interval: 2.3, 17.6). Any level of executive dysfunction increased the odds of inadequately controlled diabetes compared to patients in the best quintile of executive functioning (odds ratio = 3.6; 95% confidence interval: 1.58, 8.35). Conclusions: Memory impairment and executive dysfunction were associated with inadequately controlled diabetes. Though causal inferences are not robust in a cross-sectional study, we suggest that cognitive dysfunction may interfere with diabetes management and that inadequate diabetic control may contribute to cognitive dysfunction.
Risk and Efficacy in Biomedical Media Representations of Herbal Medicine and Complementary and Alternative Medicine (CAM)
Authors: Lewis Monique
Published: June 2011

The objective of the research was to map the discourse about herbal medicine in Australia’s primary medical journal, the Medical Journal of Australia, over 4 decades. Manifest content analysis of 148 articles about herbal or complementary and alternative medicine (CAM) in journal articles from 1966 to 2008 was undertaken. Issues of risk dominated the discourse about herbal medicine in the journal (70%), with a focus on adverse events (42%) as the most significant risk of herbal and other complementary medicines. Toxicity (23%) and drug interactions (18%) were the most frequently mentioned specific risk items. Items that acknowledged efficacy (32%) outweighed those suggesting ineffectiveness (11%). Case reports, reviews, research articles, and letters all had risk frequencies of more than 70%. Review articles and research articles had a high rate of reference to both risk and benefit. Review articles were found to have greater reference to benefit than risk. Possible reasons for these findings are discussed.
A survey of the transmission of infectious diseases/infections between wild and domestic ungulates in Europe
Authors: Martin Claire , Pastoret Paul-Pierre , Brochier Bernard , Humblet Marie-France , Saegerman Claude
Published: June 2011

The domestic animals/wildlife interface is becoming a global issue of growing interest. However, despite studies on wildlife diseases being in expansion, the epidemiological role of wild animals in the transmission of infectious diseases remains unclear most of the time. Multiple diseases affecting livestock have already been identified in wildlife, especially in wild ungulates. The first objective of this paper was to establish a list of infections already reported in European wild ungulates. For each disease/infection, three additional materials develop examples already published, specifying the epidemiological role of the species as assigned by the authors. Furthermore, risk factors associated with interactions between wild and domestic animals and regarding emerging infectious diseases are summarized. Finally, the wildlife surveillance measures implemented in different European countries are presented. New research areas are proposed in order to provide efficient tools to prevent the transmission of diseases between wild ungulates and livestock.
Primary Neuronal Precursors in Adult Crayfish Brain: Replenishment from a Non-neuronal Source
Authors: Benton Jeanne L , Zhang Yi , Kirkhart Colleen R , Sandeman David C , Beltz Barbara S
Published: June 2011

Background

Adult neurogenesis, the production and integration of new neurons into circuits in the brains of adult animals, is a common feature of a variety of organisms, ranging from insects and crustaceans to birds and mammals. In the mammalian brain the 1st-generation neuronal precursors, the astrocytic stem cells, reside in neurogenic niches and are reported to undergo self-renewing divisions, thereby providing a source of new neurons throughout an animal's life. In contrast, our work shows that the 1st-generation neuronal precursors in the crayfish (Procambarus clarkii) brain, which also have glial properties and lie in a neurogenic niche resembling that of vertebrates, undergo geometrically symmetrical divisions and both daughters appear to migrate away from the niche. However, in spite of this continuous efflux of cells, the number of neuronal precursors in the crayfish niche continues to expand as the animals grow and age. Based on these observations we have hypothesized that (1) the neuronal stem cells in the crayfish brain are not self-renewing, and (2) a source external to the neurogenic niche must provide cells that replenish the stem cell pool.

Results

In the present study, we tested the first hypothesis using sequential double nucleoside labeling to track the fate of 1st- and 2nd-generation neuronal precursors, as well as testing the size of the labeled stem cell pool following increasing incubation times in 5-bromo-2'-deoxyuridine (BrdU). Our results indicate that the 1st-generation precursor cells in the crayfish brain, which are functionally analogous to neural stem cells in vertebrates, are not a self-renewing population. In addition, these studies establish the cycle time of these cells. In vitro studies examining the second hypothesis show that Cell Tracker™ Green-labeled cells extracted from the hemolymph, but not other tissues, are attracted to and incorporated into the neurogenic niche, a phenomenon that appears to involve serotonergic mechanisms.

Conclusions

These results challenge our current understanding of self-renewal capacity as a defining characteristic of all adult neuronal stem cells. In addition, we suggest that in crayfish, the hematopoietic system may be a source of cells that replenish the niche stem cell pool.
Validation of the Edinburgh Claudication Questionnaire in 1st generation Black African-Caribbean and South Asian UK migrants: A sub-study to the Ethnic-Echocardiographic Heart of England Screening (E-ECHOES) study
Authors: Bennett Philip C , Lip Gregory YH , Silverman Stanley , Blann Andrew D , Gill Paramjit S
Published: June 2011

Background

We determined the diagnostic accuracy of the Edinburgh Claudication Questionnaire (ECQ) in 1st generation Black African-Caribbean UK migrants as previous diagnostic questionnaires have been found to be less accurate in this population. We also determined the diagnostic accuracy of translated versions of the ECQ in 1st generation South Asian UK migrants, as this has not been investigated before.

Methods

Subjects were recruited from the Ethnic-Echocardiographic Heart of England Screening (E-ECHOES) study, a community based screening survey for heart failure in minority ethnic groups. Translated versions of the ECQ were prepared following a recognised protocol. All participants attending screening between October 2007 and February 2009 were asked to complete the ECQ in the language of their choice (English, Punjabi, Bengali, Urdu, Hindi or Gujarati). Subjects answering positively to experiencing leg pain or discomfort on walking were asked to return to have Ankle Brachial Pressure Index (ABPI) measured.

Results

154 out of 2831 subjects participating in E-ECHOES (5.4%) were eligible to participate in this sub-study, for which 74.3% returned for ABPI assessment. Non-responders were younger than participants (59[9] vs. 65[11] years; p = 0.015). Punjabi, English and Bengali questionnaires identified participants with Intermittent Claudication, so these questionnaires were assessed. The sensitivities (SN), specificities (SP), positive (PPV) and negative (NPV) predictive values were calculated. English: SN: 50%; SP: 68%; PPV: 43%; NPV: 74%. Punjabi: SN: 50%; SP: 87%; PPV: 43%; NPV: 90%. Bengali: SN: 33%; SP: 50%; PPV: 13%; NPV: 73%. There were significant differences in diagnostic accuracy between the 3 versions (Punjabi: 83.8%; Bengali: 45%; English: 62.2%; p < 0.0001). No significant differences were found in sensitivity and specificity between illiterate and literate participants in any of the questionnaires and there was no significant different difference between those under and over 60 years of age.

Conclusions

Our findings suggest that the ECQ is not as sensitive or specific a diagnostic tool in 1st generation Black African-Caribbean and South Asian UK migrants than in the Edinburgh Artery Study, reflecting the findings of other diagnostic questionnaires in these minority ethnic groups. However this study is limited by sample size so conclusions should be interpreted with caution.
Bilateral ovarian teratoma complicated with carcinosarcoma in a 68 year old woman: a case report
Authors: Shanmughapriya S , SenthilKumar G , Balakrishnan K , Vasanthi N , Vinodhini K , Natarajaseenivasan K
Published: June 2011

Background

Composing of less than 1% of all ovarian cancers, immature teratoma is a malignancy that mainly affects the young, and they present with advanced disease. The treatment of immature teratoma is conservative primary surgery usually involving unilateral salpingo-oophorectomy followed by combination chemotherapy.

Case presentation

Here we present a case of a 68 year old woman with bilateral ovarian teratoma complicated with carcinosarcoma. The patient was diagnosed as FIGO stage IIIC. She underwent neoadjuvant chemotherapy and interval cytoreduction followed by optimal cytoreduction. The post operative management strategies and gynaecological follow up studies revealed no evidence of regional or distant metastasis.

Conclusion

Thus the choice of initial treatment should be decided in a selective fashion depending on various prognostic factors in order to increase the survival of the patients.
The Correlates of Leisure Time Physical Activity among an Adults Population from Southern Taiwan
Authors: Chen Yi-Ju , Huang Ying-Hsiang , Lu Feng-Hwa , Wu Jin-Shang , Lin Linda L , Chang Chih-Jen , Yang Yi-Ching
Published: June 2011

Background

Assessing the correlates of practicing physical activity during leisure time is important with regard to planning and designing public health strategies to increase beneficial behaviors among adult populations. Although the importance of leisure time physical activity (LTPA) is highlighted in many Western countries, there are not many publications on physical activity patterns, and even less on their correlates, in non-Western societies. The goal of this study was thus to explore the determinants influencing adults' leisure time physical activity (LTPA) in a city in southern Taiwan.

Methods

A cross-sectional population-based study was conducted in 2007, using a standardized questionnaire. Energy expenditure was dichotomized into two groups based on the recommended levels of moderate physical activity from LTPA: ≥10 or < 10 MET·hr·wk-1. Logistic regression analyses were applied to the results.

Results

A total of 762 subjects with valid data took part in the study (mean age 53.8 ± 13.8 years). In multivariate logistic regression analysis, we found the following results: Age was positively associated with LTPA. Adults with stronger perceived convenience of exercise facilities (OR = 2.04; 95%CI = 1.28-3.24) and past exercise experience in school (OR = 1.86; 95%CI= 1.19-2.91) participated in more LTPA. Subjects with more general social support (OR = 1.66;95%CI = 1.13-2.44), greater knowledge about the health benefits of exercise (OR = 1.85;95%CI = 1.25-2.74), more sports media consumption (OR = 1.94;95%CI = 1.26-2.98), and higher self-efficacy (OR = 3.99;95%CI = 2.67-5.97) were more likely to engage in LTPA. Further analysis comparing different sources of social support showed only social support from friends had a significant positive association (OR = 1.73;95%CI = 1.14-2.63) with increased LTPA.

Conclusions

LTPA in southern city of Taiwan showed some unique associations with age, socioeconomic status and media consumption that are not commonly reported in the Western World and similar associations with regards to psychosocial correlates of LTPA participation. Further studies from developing countries are warranted to highlight culture-specific differences in physical activity participation.
Evaluation of biolistic gene transfer methods in vivo using non-invasive bioluminescent imaging techniques
Authors: Xia Jixiang , Martinez Angela , Daniell Henry , Ebert Steven N
Published: June 2011

Background

Gene therapy continues to hold great potential for treating many different types of disease and dysfunction. Safe and efficient techniques for gene transfer and expression in vivo are needed to enable gene therapeutic strategies to be effective in patients. Currently, the most commonly used methods employ replication-defective viral vectors for gene transfer, while physical gene transfer methods such as biolistic-mediated ("gene-gun") delivery to target tissues have not been as extensively explored. In the present study, we evaluated the efficacy of biolistic gene transfer techniques in vivo using non-invasive bioluminescent imaging (BLI) methods.

Results

Plasmid DNA carrying the firefly luciferase (LUC) reporter gene under the control of the human Cytomegalovirus (CMV) promoter/enhancer was transfected into mouse skin and liver using biolistic methods. The plasmids were coupled to gold microspheres (1 μm diameter) using different DNA Loading Ratios (DLRs), and "shot" into target tissues using a helium-driven gene gun. The optimal DLR was found to be in the range of 4-10. Bioluminescence was measured using an In Vivo Imaging System (IVIS-50) at various time-points following transfer. Biolistic gene transfer to mouse skin produced peak reporter gene expression one day after transfer. Expression remained detectable through four days, but declined to undetectable levels by six days following gene transfer. Maximum depth of tissue penetration following biolistic transfer to abdominal skin was 200-300 μm. Similarly, biolistic gene transfer to mouse liver in vivo also produced peak early expression followed by a decline over time. In contrast to skin, however, liver expression of the reporter gene was relatively stable 4-8 days post-biolistic gene transfer, and remained detectable for nearly two weeks.

Conclusions

The use of bioluminescence imaging techniques enabled efficient evaluation of reporter gene expression in vivo. Our results demonstrate that different tissues show different expression kinetics following gene transfer of the same reporter plasmid to different mouse tissues in vivo. We evaluated superficial (skin) and abdominal organ (liver) targets, and found that reporter gene expression peaked within the first two days post-transfer in each case, but declined most rapidly in the skin (3-4 days) compared to liver (10-14 days). This information is essential for designing effective gene therapy strategies in different target tissues.
Streamlined protein expression and purification using cleavable self-aggregating tags
Authors: Xing Lei , Wu Wei , Zhou Bihong , Lin Zhanglin
Published: June 2011

Background

Recombinant protein expression and purification remains a fundamental issue for biotechnology. Recently we found that two short self-assembling amphipathic peptides 18A (EWLKAFYEKVLEKLKELF) and ELK16 (LELELKLKLELELKLK) can induce the formation of active protein aggregates in Escherichia coli (E. coli), in which the target proteins retain high enzymatic activities. Here we further explore this finding to develop a novel, facile, matrix-free protein expression and purification approach.

Results

In this paper, we describe a streamlined protein expression and purification approach by using cleavable self-aggregating tags comprising of one amphipathic peptide (18A or ELK16) and an intein molecule. In such a scheme, a target protein is first expressed as active protein aggregate, separated by simple centrifugation, and then released into solution by intein-mediated cleavage. Three target proteins including lipase A, amadoriase II and β-xylosidase were used to demonstrate the feasibility of this approach. All the target proteins released after cleavage were highly active and pure (over 90% in the case of intein-ELK16 fusions). The yields were in the range of 1.6-10.4 μg/mg wet cell pellet at small laboratory scale, which is comparable with the typical yields from the classical his-tag purification, the IMPACT-CN system (New England Biolabs, Beverly, MA), and the ELP tag purification scheme.

Conclusions

This tested single step purification is capable of producing proteins with high quantity and purity. It can greatly reduce the cost and time, and thus provides application potentials for both industrial scale up and laboratorial usage.
Insulin alleviates degradation of skeletal muscle protein by inhibiting the ubiquitin-proteasome system in septic rats
Authors: Chen Qiyi , Li Ning , Zhu Weiming , Li Weiqin , Tang Shaoqiu , Yu Wenkui , Gao Tao , Zhang Juanjuan , Li Jieshou
Published: June 2011

Hypercatabolism is common under septic conditions. Skeletal muscle is the main target organ for hypercatabolism, and this phenomenon is a vital factor in the deterioration of recovery in septic patients. In skeletal muscle, activation of the ubiquitin-proteasome system plays an important role in hypercatabolism under septic status. Insulin is a vital anticatabolic hormone and previous evidence suggests that insulin administration inhibits various steps in the ubiquitin-proteasome system. However, whether insulin can alleviate the degradation of skeletal muscle protein by inhibiting the ubiquitin-proteasome system under septic condition is unclear. This paper confirmed that mRNA and protein levels of the ubiquitin-proteasome system were upregulated and molecular markers of skeletal muscle proteolysis (tyrosine and 3-methylhistidine) simultaneously increased in the skeletal muscle of septic rats. Septic rats were infused with insulin at a constant rate of 2.4 mU.kg-1.min-1 for 8 hours. Concentrations of mRNA and proteins of the ubiquitin-proteasome system and molecular markers of skeletal muscle proteolysis were mildly affected. When the insulin infusion dose increased to 4.8 mU.kg-1.min-1, mRNA for ubiquitin, E2-14 KDa, and the C2 subunit were all sharply downregulated. At the same time, the levels of ubiquitinated proteins, E2-14KDa, and the C2 subunit protein were significantly reduced. Tyrosine and 3-methylhistidine decreased significantly. We concluded that the ubiquitin-proteasome system is important skeletal muscle hypercatabolism in septic rats. Infusion of insulin can reverse the detrimental metabolism of skeletal muscle by inhibiting the ubiquitin-proteasome system, and the effect is proportional to the insulin infusion dose.
Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots
Authors: Shih Ching-I , Lin Chien-Hung , Lin Shin-Chin , Lin Ta-Chun , Sun Kien Wen , Voskoboynikov Oleksandr , Lee Chien-Ping , Suen Yuen-Wuu
Published: June 2011

In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA) phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.
Increased expression of cystine/glutamate antiporter in multiple sclerosis
Authors: Pampliega Olatz , Domercq María , Soria Federico N , Villoslada Pablo , Rodríguez-Antigüedad Alfredo , Matute Carlos
Published: June 2011

Background

Glutamate excitotoxicity contributes to oligodendrocyte and tissue damage in multiple sclerosis (MS). Intriguingly, glutamate level in plasma and cerebrospinal fluid of MS patients is elevated, a feature which may be related to the pathophysiology of this disease. In addition to glutamate transporters, levels of extracellular glutamate are controlled by cystine/glutamate antiporter xc-, an exchanger that provides intracellular cystine for production of glutathione, the major cellular antioxidant. The objective of this study was to analyze the role of the system xc-in glutamate homeostasis alterations in MS pathology.

Methods

Primary cultures of human monocytes and the cell line U-937 were used to investigate the mechanism of glutamate release. Expression of cystine glutamate exchanger (xCT) was quantified by quantitative PCR, Western blot, flow cytometry and immunohistochemistry in monocytes in vitro, in animals with experimental autoimmune encephalomyelitis (EAE), the animal model of MS, and in samples of MS patients.

Results and discussion

We show here that human activated monocytes release glutamate through cystine/glutamate antiporter xc-and that the expression of the catalytic subunit xCT is upregulated as a consequence of monocyte activation. In addition, xCT expression is also increased in EAE and in the disease proper. In the later, high expression of xCT occurs both in the central nervous system (CNS) and in peripheral blood cells. In particular, cells from monocyte-macrophage-microglia lineage have higher xCT expression in MS and in EAE, indicating that immune activation upregulates xCT levels, which may result in higher glutamate release and contribution to excitotoxic damage to oligodendrocytes.

Conclusions

Together, these results reveal that increased expression of the cystine/glutamate antiporter system xc-in MS provides a link between inflammation and excitotoxicity in demyelinating diseases.
Escape is a more common mechanism than avidity reduction for evasion of CD8+ T cell responses in primary human immunodeficiency virus type 1 infection
Authors: Turnbull Emma L , Baalwa Joshua , Conrod Karen E , Wang Shuyi , Wei Xiping , Wong MaiLee , Turner Joanna , Pellegrino Pierre , Williams Ian , Shaw George M , Borrow Persephone
Published: June 2011

Background

CD8+ T cells play an important role in control of viral replication during acute and early human immunodeficiency virus type 1 (HIV-1) infection, contributing to containment of the acute viral burst and establishment of the prognostically-important persisting viral load. Understanding mechanisms that impair CD8+ T cell-mediated control of HIV replication in primary infection is thus of importance. This study addressed the relative extent to which HIV-specific T cell responses are impacted by viral mutational escape versus reduction in response avidity during the first year of infection.

Results

18 patients presenting with symptomatic primary HIV-1 infection, most of whom subsequently established moderate-high persisting viral loads, were studied. HIV-specific T cell responses were mapped in each individual and responses to a subset of optimally-defined CD8+ T cell epitopes were followed from acute infection onwards to determine whether they were escaped or declined in avidity over time. During the first year of infection, sequence variation occurred in/around 26/33 epitopes studied (79%). In 82% of cases of intra-epitopic sequence variation, the mutation was confirmed to confer escape, although T cell responses were subsequently expanded to variant sequences in some cases. In contrast, < 10% of responses to index sequence epitopes declined in functional avidity over the same time-frame, and a similar proportion of responses actually exhibited an increase in functional avidity during this period.

Conclusions

Escape appears to constitute a much more important means of viral evasion of CD8+ T cell responses in acute and early HIV infection than decline in functional avidity of epitope-specific T cells. These findings support the design of vaccines to elicit T cell responses that are difficult for the virus to escape.
Conformational alterations in the CD4 binding cavity of HIV-1 gp120 influencing gp120-CD4 interactions and fusogenicity of HIV-1 envelopes derived from brain and other tissues
Authors: Gray Lachlan , Sterjovski Jasminka , Ramsland Paul A , Churchill Melissa J , Gorry Paul R
Published: June 2011

Background

CD4-binding site (CD4bs) alterations in gp120 contribute to HIV-1 envelope (Env) mediated fusogenicity and the ability of gp120 to utilize low levels of cell-surface CD4. In a recent study, we constructed three-dimensional models of gp120 to illustrate CD4bs conformations associated with enhanced fusogenicity and enhanced CD4-usage of a modestly-sized panel of blood-derived HIV-1 Envs (n = 16). These conformations were characterized by a wider aperture of the CD4bs cavity, as constrained by the inner-most atoms at the gp120 V1V2 stem and the V5 loop. Here, we sought to provide further validation of the utility of these models for understanding mechanisms that influence Env function, by characterizing the structure-function relationships of a larger panel of Envs derived from brain and other tissues (n = 81).

Findings

Three-dimensional models of gp120 were generated by our recently validated homology modelling protocol. Analysis of predicted CD4bs structures showed correlations between the aperture width of the CD4bs cavity and ability of the Envs to mediate cell-cell fusion, scavenge low-levels of cell-surface CD4, bind directly to soluble CD4, and bind to the Env mAb IgG1b12 whose epitope overlaps the gp120 CD4bs. These structural alterations in the CD4bs cavity were associated with repositioning of the V5 loop.

Conclusions

Using a large, independent panel of Envs, we can confirm the utility of three-dimensional gp120 structural models for illustrating CD4bs alterations that can affect Env function. Furthermore, we now provide new evidence that these CD4bs alterations augment the ability of gp120 to interact with CD4 by increasing the exposure of the CD4bs.
Thymic plasmacytoid dendritic cells are susceptible to productive HIV-1 infection and efficiently transfer R5 HIV-1 to thymocytes in vitro
Authors: Evans Vanessa A , Lal Luxshimi , Akkina Ramesh , Solomon Ajantha , Wright Edwina , Lewin Sharon R , Cameron Paul U
Published: June 2011

Background

HIV-1 infection of the thymus contributes to the defective regeneration and loss of CD4+T cells in HIV-1-infected individuals. As thymic dendritic cells (DC) are permissive to infection by HIV-1, we examined the ability of thymic DC to enhance infection of thymocytes which may contribute to the overall depletion of CD4+T cells. We compared productive infection in isolated human thymic and blood CD11c+myeloid DC (mDC) and CD123+plasmacytoid DC (pDC) using enhanced green fluorescent protein (EGFP) CCR5 (R5)-tropic NL(AD8) and CXCR4 (X4)-tropic NL4-3 HIV-1 reporter viruses. Transfer of productive HIV-1 infection from thymic mDC and pDC was determined by culturing these DC subsets either alone or with sorted thymocytes.

Results

Productive infection was observed in both thymic pDC and mDC following exposure to R5 HIV-1 and X4 HIV-1. Thymic pDC were more frequently productively infected by both R5 and X4 HIV-1 than thymic mDC (p = 0.03; n = 6). Thymic pDC efficiently transferred productive R5 HIV-1 infection to both CD3hi(p = 0.01; mean fold increase of 6.5; n = 6) and CD3lothymocytes (mean fold increase of 1.6; n = 2). In comparison, transfer of productive infection by thymic mDC was not observed for either X4 or R5 HIV-1.

Conclusions

The capacity of thymic pDC to efficiently transfer R5 HIV-1 to both mature and immature thymocytes that are otherwise refractory to R5 virus may represent a pathway to early infection and impaired production of thymocytes and CD4+T cells in HIV-1-infected individuals.
Client preferences and acceptability for medical abortion and MVA as early pregnancy termination method in Northwest Ethiopia
Authors: Woldetsadik Mulatu A , Sendekie Tegbar Y , White Mary T , Zegeye Desalegn T
Published: June 2011

Background

Increasing access to safe abortion services is the most effective way of preventing the burden of unsafe abortion, which is achieved by increasing safe choices for pregnancy termination. Medical abortion for termination of early abortion is said to safe, effective, and acceptable to women in several countries. In Ethiopia, however, medical methods have, until recently, never been used. For this reason it is important to assess women's preferences and the acceptability of medical abortion and manual vacuum aspiration (MVA) in the early first trimester pregnancy termination and factors affecting acceptability of medical and MVA abortion services.

Methods

A prospective study was conducted in two hospitals and two clinics from March 2009 to November 2009. The study population consisted of 414 subjects over the age of 18 with intrauterine pregnancies of up to 63 days' estimated gestation. Of these 251 subjects received mifepristone and misoprostol and 159 subjects received MVA. Questionnaires regarding expectations and experiences were administered before the abortion and at the 2-week follow-up visit.

Results

The study groups were similar with respect to age, marital status, educational status, religion and ethnicity. Their mean age was about 23, majority in both group completed secondary education and about half were married. Place of residence and duration of pregnancy were associated with method choice. Subjects undergoing medical abortions reported significantly greater satisfaction than those undergoing surgical abortions (91.2% vs 82.4%; P < .001). Of those women who had medical abortion, (83.3%) would choose the method again if needed, and (77.4%) of those who had MVA would also choose the method again. Ninety four percent of women who had medical abortion and 86.8% of those who had MVA would recommend the method to their friends.

Conclusions

Women receiving medical abortion were more satisfied with their method and more likely to choose the same method again than were subjects undergoing surgical abortion. We conclude that medical abortion can be used widely as an alternative method for early pregnancy termination.
FXTAS is rare among Portuguese patients with movement disorders: FMR1 premutations may be associated with a wider spectrum of phenotypes
Authors: Seixas Ana I. , Vale José , Jorge Paula , Marques Isabel , Santos Rosário , Alonso Isabel , Fortuna Ana M. , Pinto-Basto Jorge , Coutinho Paula , Margolis Russell L. , Sequeiros Jorge , Silveira Isabel
Published: June 2011

The fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by expansions of 55-200 CGG repeats in the 5'UTR of the FMR1 gene. These FMR1 premutation expansions have relatively high frequency in the general population. To estimate the frequency of FMR1 premutations among Portuguese males with non-familial, late-onset movement disorders of unknown etiology, we assessed CGG repeat size in males with disease onset after the age of 50 and negative or unknown family history for late-onset movement disorders, who were sent for SCA, HD, or PD genetic testing at a reference laboratory. The selected patients had a primary clinical diagnosis based on one of the following cardinal features of FXTAS: ataxia, tremor, or cognitive decline. A total of 86 subjects were genotyped for the CGG repeat in the FMR1 gene. We detected one patient with an expansion in the premutation range. The frequency of FMR1 premutations was 1.9% (1/54) in our group of patients with ataxia as the primary clinical feature, and 1.2% (1/86) in the larger movement disorders group. In the family of the FXTAS case, premutation-transmitting females presented a history of psychiatric symptoms, suggesting that, given the wide phenotypical expression of the premutation in females, neuropsychiatric surveillance is necessary. In conclusion, genetic testing for FXTAS should be made available to patients with adult-onset movement disorders to enable adequate genetic counseling to family members.
Molecular evolution of rbcL in three gymnosperm families: identifying adaptive and coevolutionary patterns
Authors: Sen Lin , Fares Mario A , Liang Bo , Gao Lei , Wang Bo , Wang Ting , Su Ying-Juan
Published: June 2011

Background

The chloroplast-localized ribulose-1, 5-biphosphate carboxylase/oxygenase (Rubisco), the primary enzyme responsible for autotrophy, is instrumental in the continual adaptation of plants to variations in the concentrations of CO2. The large subunit (LSU) of Rubisco is encoded by the chloroplast rbcL gene. Although adaptive processes have been previously identified at this gene, characterizing the relationships between the mutational dynamics at the protein level may yield clues on the biological meaning of such adaptive processes. The role of such coevolutionary dynamics in the continual fine-tuning of RbcL remains obscure.

Results

We used the timescale and phylogenetic analyses to investigate and search for processes of adaptive evolution in rbcL gene in three gymnosperm families, namely Podocarpaceae, Taxaceae and Cephalotaxaceae. To understand the relationships between regions identified as having evolved under adaptive evolution, we performed coevolutionary analyses using the software CAPS. Importantly, adaptive processes were identified at amino acid sites located on the contact regions among the Rubisco subunits and on the interface between Rubisco and its activase. Adaptive amino acid replacements at these regions may have optimized the holoenzyme activity. This hypothesis was pinpointed by evidence originated from our analysis of coevolution that supported the correlated evolution between Rubisco and its activase. Interestingly, the correlated adaptive processes between both these proteins have paralleled the geological variation history of the concentration of atmospheric CO2.

Conclusions

The gene rbcL has experienced bursts of adaptations in response to the changing concentration of CO2 in the atmosphere. These adaptations have emerged as a result of a continuous dynamic of mutations, many of which may have involved innovation of functional Rubisco features. Analysis of the protein structure and the functional implications of such mutations put forward the conclusion that this evolutionary scenario has been possible through a complex interplay between adaptive mutations, often structurally destabilizing, and compensatory mutations. Our results unearth patterns of evolution that have likely optimized the Rubisco activity and uncover mutational dynamics useful in the molecular engineering of enzymatic activities.

Reviewers

This article was reviewed by Prof. Christian Blouin (nominated by Dr W Ford Doolittle), Dr Endre Barta (nominated by Dr Sandor Pongor), and Dr Nicolas Galtier.
Low early ototoxicity rates for pediatric medulloblastoma patients treated with proton radiotherapy
Authors: Moeller Benjamin J , Chintagumpala Murali , Philip Jimmy J , Grosshans David R , McAleer Mary F , Woo Shiao Y , Gidley Paul W , Vats Tribhawan S , Mahajan Anita
Published: June 2011

Background

Hearing loss is common following chemoradiotherapy for children with medulloblastoma. Compared to photons, proton radiotherapy reduces radiation dose to the cochlea for these patients. Here we examine whether this dosimetric advantage leads to a clinical benefit in audiometric outcomes.

Methods

From 2006-2009, 23 children treated with proton radiotherapy for medulloblastoma were enrolled on a prospective observational study, through which they underwent pre- and 1 year post-radiotherapy pure-tone audiometric testing. Ears with moderate to severe hearing loss prior to therapy were censored, leaving 35 ears in 19 patients available for analysis.

Results

The predicted mean cochlear radiation dose was 30 60Co-Gy Equivalents (range 19-43), and the mean cumulative cisplatin dose was 303 mg/m2 (range 298-330). Hearing sensitivity significantly declined following radiotherapy across all frequencies analyzed (P < 0.05). There was partial sparing of mean post-radiation hearing thresholds at low-to-midrange frequencies and, consequently, the rate of high-grade (grade 3 or 4) ototoxicity at 1 year was favorable (5%). Ototoxicity did not correlate with predicted dose to the auditory apparatus for proton-treated patients, potentially reflecting a lower-limit threshold for radiation effect on the cochlea.

Conclusions

Rates of high-grade early post-radiation ototoxicity following proton radiotherapy for pediatric medulloblastoma are low. Preservation of hearing in the audible speech range, as observed here, may improve both quality of life and cognitive functioning for these patients.
Thrombospondin 1 in hypoxia-conditioned media blocks the growth of human microvascular endothelial cells and is increased in systemic sclerosis tissues
Authors: Morgan-Rowe Luke , Nikitorowicz Joanna , Shiwen Xu , Leask Andrew , Tsui Janice , Abraham David , Stratton Richard
Published: June 2011

Background

Systemic sclerosis (SSc) is a chronic inflammatory autoimmune disease characterised by vascular dysfunction and damage, excess collagen deposition and subsequent organ manifestations. Vasculopathy is an early feature of the disease which leads to a chronic hypoxic environment in the tissues. Paradoxically, there is a lack of angiogenesis. We hypothesised that this may in part be due to a nonphysiological, overriding upregulation in antiangiogenic factors produced by the hypoxic tissues. We considered thrombospondin 1 (TSP-1) as a candidate antiangiogenic factor.

Results

Conditioned media from human microvascular endothelial cells cultured in both normoxic and hypoxic environments were able to block endothelial cell proliferation, with the latter environment having a more profound effect. Filtration to remove > 100-kDa proteins or heparin-binding proteins from the conditioned media eliminated their antiproliferative effect. TSP-1 was expressed in high concentrations in the hypoxic media, as was vascular endothelial growth factor (VEGF). Depletion of TSP-1 from the media by immunoprecipitation reduced the antiproliferative effect. We then show that, in a dose-dependent fashion, recombinant TSP-1 blocks the proliferation of endothelial cells. Immunohistochemistry of skin biopsy material revealed that TSP-1 expression was significantly higher throughout the skin of patients with SSc compared with healthy controls.

Conclusions

Despite the environment of chronic tissue hypoxia in SSc, there is a paradoxical absence of angiogenesis. This is thought to be due in part to aberrant expression of antiangiogenic factors, including TSP-1. We have demonstrated that TSP-1 is released in high concentrations by hypoxic endothelial cells. The conditioned media from these cells is able to block proliferation and induce apoptosis in microvascular endothelial cells, an effect that is reduced when TSP-1 is immunoprecipitated out. Further, we have shown that recombinant TSP-1 is able to block proliferation and induce apoptosis at concentrations consistent with those found in the plasma of patients with SSc and that its effect occurs in the presence of elevated VEGF levels. Taken together, these data are consistent with a model wherein injured microvascular cells in SSc fail to repair because of dysregulated induction of TSP-1 in the hypoxic tissues.