111 research outputs found
A quantitative polymerase chain reaction-enzyme immunoassay for accurate measurements of human papillomavirus type 16 DNA levels in cervical scrapings
A quantitative polymerase chain reaction-enzyme immunoassay (Q-PCR-EIA) was developed to measure the amount of human papillomavirus (HPV) 16 DNA per genome equivalent in cervical scrapings. The quantitative approach was based on a combined competitive PCR for both HPV 16, using the general primer GP5+/6+ PCR, and β-globin DNA. The two competitive PCRs involve co-amplification of target sequences and exogenously added DNA constructs carrying a rearranged 30 bp sequence in the probe-binding region. The accuracy of quantification by combining the two competitive PCR assays was validated on mixtures of HPV 16 containing cervical cancer cells of CaSki and SiHa cell lines. Comparison of this fully quantitative PCR assay with two semi-quantitative HPV PCR assays on a series of crude cell suspensions from HPV 16 containing cervical scrapings revealed remarkable differences in the calculated relative HPV load between samples. We found evidence that correction for both intertube variations in PCR efficiency and number of input cells/integrity of DNA significantly influence the outcome of studies on viral DNA load in crude cell suspensions of cervical scrapings. Therefore, accurate measurements on viral DNA load in cervical scrapings require corrections for these phenomena, which can be achieved by application of this fully quantitative approach. © 1999 Cancer Research Campaig
Efficient Sparse Coding in Early Sensory Processing: Lessons from Signal Recovery
Sensory representations are not only sparse, but often overcomplete: coding units significantly outnumber the input units. For models of neural coding this overcompleteness poses a computational challenge for shaping the signal processing channels as well as for using the large and sparse representations in an efficient way. We argue that higher level overcompleteness becomes computationally tractable by imposing sparsity on synaptic activity and we also show that such structural sparsity can be facilitated by statistics based decomposition of the stimuli into typical and atypical parts prior to sparse coding. Typical parts represent large-scale correlations, thus they can be significantly compressed. Atypical parts, on the other hand, represent local features and are the subjects of actual sparse coding. When applied on natural images, our decomposition based sparse coding model can efficiently form overcomplete codes and both center-surround and oriented filters are obtained similar to those observed in the retina and the primary visual cortex, respectively. Therefore we hypothesize that the proposed computational architecture can be seen as a coherent functional model of the first stages of sensory coding in early vision
Trapped electron coupled to superconducting devices
We propose to couple a trapped single electron to superconducting structures
located at a variable distance from the electron. The electron is captured in a
cryogenic Penning trap using electric fields and a static magnetic field in the
Tesla range. Measurements on the electron will allow investigating the
properties of the superconductor such as vortex structure, damping and
decoherence. We propose to couple a superconducting microwave resonator to the
electron in order to realize a circuit QED-like experiment, as well as to
couple superconducting Josephson junctions or superconducting quantum
interferometers (SQUIDs) to the electron. The electron may also be coupled to a
vortex which is situated in a double well potential, realized by nearby pinning
centers in the superconductor, acting as a quantum mechanical two level system
that can be controlled by a transport current tilting the double well
potential. When the vortex is trapped in the interferometer arms of a SQUID,
this would allow its detection both by the SQUID and by the electron.Comment: 13 pages, 5 figure
The role of ongoing dendritic oscillations in single-neuron dynamics
The dendritic tree contributes significantly to the elementary computations a neuron performs while converting its synaptic inputs into action potential output. Traditionally, these computations have been characterized as temporally local, near-instantaneous mappings from the current input of the cell to its current output, brought about by somatic summation of dendritic contributions that are generated in spatially localized functional compartments. However, recent evidence about the presence of oscillations in dendrites suggests a qualitatively different mode of operation: the instantaneous phase of such oscillations can depend on a long history of inputs, and under appropriate conditions, even dendritic oscillators that are remote may interact through synchronization. Here, we develop a mathematical framework to analyze the interactions of local dendritic oscillations, and the way these interactions influence single cell computations. Combining weakly coupled oscillator methods with cable theoretic arguments, we derive phase-locking states for multiple oscillating dendritic compartments. We characterize how the phase-locking properties depend on key parameters of the oscillating dendrite: the electrotonic properties of the (active) dendritic segment, and the intrinsic properties of the dendritic oscillators. As a direct consequence, we show how input to the dendrites can modulate phase-locking behavior and hence global dendritic coherence. In turn, dendritic coherence is able to gate the integration and propagation of synaptic signals to the soma, ultimately leading to an effective control of somatic spike generation. Our results suggest that dendritic oscillations enable the dendritic tree to operate on more global temporal and spatial scales than previously thought
Barriers to HPV self-sampling and cytology among low-income indigenous women in rural areas of a middle-income setting: a qualitative study.
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.BACKGROUND: Data is needed about barriers to self-collection of Human Papillomavirus (HPV) samples and cytology among low-income, disadvantaged women living in rural areas of lower-income countries as these women are at increased risk of cervical cancer mortality. METHODS: Individual interviews (n = 29), focus groups (n = 7, 5-11 participants) and discussion groups (n = 2, 18-25 participants) were organized with women from three indigenous ethnic groups residing in rural areas in Mexico, after they were provided with free, self-sampled HPV tests. These groups are low-income, underserved by healthcare and have historically been on the receiving end of racism and social exclusion. Descriptive, qualitative content analysis was done, including two cycles of coding. RESULTS: Interview and focus/discussion group data indicate women had limited understanding of HPV's role in cervical cancer etiology. They identified HPV's existence, that cytology detects cervical cancer, the need for regular testing and that cervical cancer is sexually transmitted. Organizational barriers to clinic-based cytology included irregular supplies of disposable speculums, distance to clinics and lack of clear communication by healthcare personnel. Women considered self-collected HPV-testing easy, less embarrassing and less painful than cytology, an opportunity for self-care and most felt they understood how to take a self-sample after a 20-min explanation. Some women feared hurting themselves when taking the self-sample or that they would take the sample incorrectly, which they worried would make the test useless. Attending HPV-testing in groups facilitated use by allowing women to discuss their doubts and fears before doing self-collection of the sample or to ask other women who were the first to do the self-sampling what the experience had been like (whether it hurt and how easy it was). Lack of indoor bathrooms was a barrier to doing HPV self-sampling at home, when those homes were resource-poor (one-room dwellings). CONCLUSIONS: Low-income, indigenous Mexican women residing in rural, underserved areas identified their need for cervical cancer screening but encountered multiple barriers to cytology-based screening. They found a number of advantages of HPV self-sampled tests. Employing self-collected HPV-testing instead of cytology could resolve some but not all gender-related, organizational or technical quality-of-care issues within cervical cancer detection and control programs.The Hybrid Capture 2 HPV tests used in this study were generously donated by Digene Corporation. Financial support for fieldwork was provided by the National HIV and AIDS Prevention and Control Center (CENSIDA) and the National Institute of Public Health, Mexico (INSP)
Human papillomavirus testing as an optional screening tool in low-resource settings of Latin America: experience from the Latin American Screening study
Hybrid capture II (HC II) test for oncogenic human papillomaviruses (HPV) was carried out in a cohort of 4284 women at their first clinical visit. Overall prevalence of HPV was 17.1%, decreasing with age from 33.9% among women below 20 years to only 11.0% among those older than 41 years. HPV prevalence was significantly higher among current smokers (odds ratio [OR] ¼ 1.31; 95% CI 1.1–1.6), in women with two or more lifetime sexual partners (OR ¼ 1.9; 95% CI 1.6–2.4), and those women with two or more sexual partners during the past 12 months prior to examination (OR ¼ 1.6; 95% CI 1.2–2.2). HPV detection increased in parallel with increasing cytologic abnormality, being highest in women with high-grade squamous intraepithelial lesion (P ¼ 0.001). Specificity of the HPV test in detecting histologically confirmed cervical disease was 85% (95% CI 83.9–86.1). Sensitivity of the HPV test in detecting histologic abnormalities increased
in parallel with disease severity, ranging from 51.5% for cervical intraepithelial neoplasia (CIN) 1 to 96.5% for CIN 3 and 100.0% for cancer, with respective decline of positive predictive value. These data suggest
that HPV testing with HC II assay might be a viable screening tool among this population with relatively high prevalence of cervical disease
Evaluation of visual inspection with acetic acid (VIA), Lugol’s iodine (VILI), cervical cytology and HPV testing as cervical screening tools in Latin America
Objectives: To assess the performance indicators of visual inspection with acetic acid (VIA) and visual
inspection with Lugol’s iodine (VILI) in four Latin American centres participating in the ongoing Latin
AMerican Screening (LAMS) study, in settings with moderate incidence of cervical disease and with
poorly to moderately well-organized cervical cancer screening.
Setting: Three Brazilian centres (São Paulo, Campinas and Porto Alegre) and one Argentine centre
(Buenos Aires) recruited a total of 11,834 healthy women to undergo VIA, VILI, conventional Pap
smear and Hybrid Capture II (HCII).
Methods: Women who had a positive result from any of these tests were subjected to colposcopy and
biopsies (if necessary), and women with high-grade cervical intraepithelial neoplasia (CIN) were
properly treated. To control for verification bias, 5% of women with normal tests were referred for
colposcopy, as were 20% of HCII-negative women.
Results: Data on VIA (n = 11,834), VILI (n = 2994), conventional Pap smear (n = 10,138) and HCII
(n = 4195) were available for test comparisons, calculating sensitivity, specificity, and positive and
negative predictive values. Overall test positivity was 11.6% for VIA, 23.0% for VILI, 2.2% for Pap
smear (LSIL threshold), 1.1% for Pap smear (HSIL threshold) and 17.1% for HCII. VIA was positive in
61.8% of the women with CIN 1, 57.0% of those with CIN 2, 35.0% of women with CIN 3 and in 21
of 28 (75%) of women with cancer. Approximately 10% of women with no detectable disease had an
abnormal VIA. Regarding VILI, 83.3% of women diagnosed with CIN 1 and 62.5% of those with CIN
3 had an abnormal test. VILI failed to detect one of three cases of cancer. Both the sensitivity, specificity
and positive predictive value of VIA and VILI in detecting CIN 2 or CIN 3 could be significantly
improved depending on the combination with Pap smear or HCII (sensitivity up to 100.0% and
specificity up to 99.8%).
Conclusions: The LAMS study failed to reproduce the performance figures obtained with VIA and VILI
(as stand-alone tests) in some other settings, where the prevalence of cervical disease was higher.
However, a combined use of VIA or VILI with the Pap test or HCII allowed specific detection of cervical
abnormalities.European Union (EU) - INCO-DEV Programme - Contract# ICA4-CT-2001-10013
Safety of screening with Human papillomavirus testing for cervical cancer at three-year intervals in a high-risk population: experience from the LAMS study
To assess whether human papillomavirus (HPV) testing is a safe enough approach to warrant extension of the screening intervals of baseline Papanicolaou (Pap)-/HPV- women in low-income settings.European Commission, INCO-DEV Programme (Contract # ICA4-CT-2001-10013). The generous contribution from DIGENE Inc. (USA) donating the HC 2 test
Thin-layer liquid-based cervical cytology and PCR for detecting and typing human papillomavirus DNA in Flemish women
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