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PubMed2006

SNPmasker: automatic masking of SNPs and repeats across eukaryotic genomes.

SNPmasker is a comprehensive web interface for masking large eukaryotic genomes. The program is designed to mask SNPs from recent dbSNP database and to mask the repeats with two alternative programs. In addition to the SNP masking, we also offer population-specific substitution of SNP alleles in genomic sequence according to SNP frequencies in HapMap Phase II data. The input to SNPmasker can be defined in chromosomal coordinates or inserted as a sequence. The sequences masked by our web server are most useful as a preliminary step for different primer and probe design tasks. The service is available at http://bioinfo.ebc.ee/snpmasker/ and is free for all users.

Alleles↗
PubMedDate not supplied

Photographic unsharp masking in chest radiography.

A photographic unsharp masking technique for improving the latitude of chest radiographs without sacrificing image contrast or detail is described. An unsharp mask film, prepared from a scout film of the patient's chest, is placed between the film and the front (entrance) screen in the cassette. A second radiograph then is recorded using technique factors that provide a well-penetrated view of the central mediastinum, etc. The unsharp mask absorbs light from the screen in those areas of the chest that normally are well penetrated, preventing overexposure of these areas and resulting in an improved balance of densities across the chest image. Improvement of contrast by a factor of 2 is demonstrated for mediastinal and retrocardiac structures with no loss of contrast in the central lung fields. Nodule detection studies with a chest phantom and simulated nodules suggest that a single unsharp masked film provides higher nodule detection rates than a pair of films consisting of a normally penetrated and an overpenetrated view, possibly because of facilitation of visual search patterns and contrast/brightness adaptation mechanisms of the visual system. Initial clinical studies indicate that unsharp masking may provide additional useful clinical information.

Humans↗
PubMed2004

Masked hypertension: how can the condition be detected?

Recent evidence demonstrates that masked hypertension is a significant predictor of cardiovascular disease, but the problem for clinical practice is how to identify these patients. Furthermore, the prevalence of masked hypertension in the general population or in subjects with transient blood pressure elevation is still unknown. Data obtained in several cross-sectional studies have demonstrated large differences in the prevalence of masked hypertension, with prevalence rates from a low of 8% to a high of 49%. Two population-based studies performed in Italy and in Japan report prevalence of 9% and of 13.4%, respectively. A 49% frequency of masked hypertension has been found among subjects with transiently elevated clinic blood pressure. Several factors can selectively raise ambulatory blood pressure including age, sex, smoking, alcohol use, contraceptive use in women, and sedentary habits. Reactivity to daily life stressors and behavioural factors are other important determinants of ambulatory blood pressure. On the basis of the available evidence, masked hypertension should be searched for in individuals who are more likely to have this condition or are at increased risk of cardiovascular complications including diabetic individuals and subjects with kidney disease. Further research is needed to determine whether the use of ambulatory blood pressure monitoring is cost-effective in these subjects.

Blood Pressure Monitoring, Ambulatory↗
PubMed2005

White-coat hypertension and masked hypertension in children.

The use of ambulatory blood pressure monitoring in addition to the conventional office measurements makes possible the detection of individuals with white-coat hypertension and masked hypertension. In children referred for elevated blood pressure, both these phenomena appear to be common (10-15% for each). In a population of healthy children, white-coat hypertension appears to be as common as hypertension, whereas masked hypertension appears to be more common than white-coat hypertension or hypertension. In children with persistent white-coat or masked hypertension, assessment of target organ damage by echocardiography is required. Preliminary evidence suggests that, in contrast to white-coat hypertension, which is not associated with target organ damage, masked hypertension in children is associated with increased left ventricular mass. Children with masked hypertension should be followed up and possibly treated for hypertension if the phenomenon persists or there is evidence of target organ damage.

Adolescent↗
PubMed2006

Predictive factors for masked hypertension within a population of controlled hypertensives.

CONTEXT: Prevalence of masked hypertension (MH) is far from negligible reaching 40% in some studies. The SHEAF study (Self measurement of blood pressure at Home in the Elderly: Assessment and Follow-Up) and others clearly showed that masked hypertension (MH) as detected by home blood pressure measurement (HBPM) is associated with poor cardiovascular prognosis. OBJECTIVE: Systematic HBPM to detect MH is not yet routine. The aim of this work is to better define the clinical profile of masked hypertensives within a population with controlled office blood pressure (BP) and the factors associated with a higher prevalence of MH. MATERIALS AND METHODS: BP was measured at the clinic by the doctor and at home by the patient himself. Risk factors for MH were analysed in a cohort of 1150 treated hypertensive patients over the age of 60 (mean age 70 +/- 6.5, 48.9% men) with controlled office BP. (SBP < 140 mmHg and DBP < 90 mmHg). RESULTS: 463 patients (40%) were masked hypertensives (SBP > or = 135 mmHg or DBP > or = 85 mmHg at home). Three parameters were associated with MH (odds ratio OR): office SBP (OR = 1.110), male gender (OR = 2.214) and age (OR = 1.031). Decision trees showed a 130 mmHg SBP was an efficient threshold to propose HBPM with a higher probability to detect MH. Subsequent variables were male gender and age over 70 in males. CONCLUSION: To detect masked hypertension, it would be logical to first of all select patients whose office SBP is between 130 and 140 mmHg.

Adolescent↗
PubMed1994

The effect of the timing, quality and quantity of sleep upon the depression (masking) of body temperature on an irregular sleep/wake schedule.

Eight subjects were studied on an irregular sleep/wake schedule which was designed so that prior wake time and the time of day when 4-h sleep periods were taken were both balanced. Rectal temperature and the sleep EEG were measured throughout the 8-d protocol. A purification method was used to estimate the depression of rectal temperature (masking) caused by the first and second halves of each 4-h sleep period. On average this was 0.187 +/- 0.015 degrees C during the first 2 h and 0.262 +/- 0.017 degrees C during the second 2 h. Masking increases beyond the first 2 h of sleep, but any effects due to the phase of the rectal temperature when sleep is taken are very weak. However, masking did increase (that is, the temperature was depressed more) when the amount of prior wake time was greater than 4 h. When the effects of sleep content variables were considered also, masking was still greater in the second half of sleep and tended to increase with the amount of slow-wave sleep, but it decreased with increasing amounts of time awake during a sleep period (sleep latency or sleep discontinuity). Some implications of these results for the mechanism of sleep-induced masking are considered.

Journal Article↗
PubMed2005

Recognition of affect in facial expression using the Noh Mask Test: comparison of individuals with schizophrenia and normal controls.

The purpose of the present study was to compare facial expression recognition in individuals with schizophrenia and normal controls using the Noh Mask Test. Fifteen men with schizophrenia and 15 normal controls were presented with a photograph of a Noh mask rotated either upward or downward from the neutral front-facing position, and an emotion label, and were requested to judge whether the expression of the mask was congruent with the indicated emotion. Using multidimensional scaling, the facial expression of the Noh mask recognized by the patients and the healthy controls was analyzed in 3-D: (i) Rejection-Attention; (ii) Pleasant-Unpleasant; and (iii) Awakening-Relaxation. Individuals with schizophrenia had difficulty recognizing that others had intentions of harming them. The Noh Mask Test was found to be useful in discriminating between individuals with schizophrenia and controls in the recognition of facial expression (discriminant ratio: 99.9%).

Adult↗
PubMedDate not supplied

Influence of vaporizer setting on mask induction of dogs with isoflurane using an in-circuit vaporizer.

The speed of mask induction using an in-circuit vaporizer may be influenced by vaporizer setting. To investigate this in clinical patients, 18 dogs were randomly assigned to one of three groups. Each dog was premedicated and then mask induced with isoflurane using a Stephen's in-circuit vaporizer set at 1/2, 3/4, or full ON. We determined inspired isoflurane and oxygen concentrations at the level of the mask, respiratory rate, resistance to mask induction, and time to intubation. No significant differences were found between groups in resistance to induction or in time to intubation. At settings of 3/4 and full ON, inspired isoflurane concentrations at time of intubation ranged from 3.3% to 8.25%, and were significantly higher than those resulting from the 1/2 setting (range 2.1% to 4.6%). We conclude that it may be preferable to avoid settings greater than 1/2 when using the Stephen's vaporizer for mask induction because of the potential adverse effects of high inspired inhalant anesthetic concentrations. In addition, use of higher vaporizer settings may not significantly speed induction.

Animals↗
PubMed2004

Supersequences of masks for oligo-chips.

On a very small surface, a chip, several thousands of oligonucleotides, can be synthesized using a mask technology. Given a set of oligos, the problems tackled here are: What is the minimum number of masks necessary to synthesize one copy of each oligo? How long will be the series of masks if each oligo is synthesized twice, such that the two copies are realized with two completely different series of masks? We establish that, for 20,000 oligos of 20 bases a single copy can be synthesized with around 67 masks and for two copies with less than the double.

Algorithms↗
PubMed1983

Clinical evaluation of unsharp masking and slit scanning techniques in chest radiography.

Conventional, unsharp masking, and slit-mask (combining slit radiography and unsharp masking) techniques were compared in a clinical nodule detection study in cancer patients who were at risk for metastatic lung disease. Unsharp masking improved detection rates for nodules located in poorly penetrated areas of the chest (25% vs. 52%), with no difference in detection rates for other areas of the image and no change in false-positive detection rates. Results with the slit-mask technique did not differ significantly from those obtained with conventional techniques. In general, the differences in nodule detection rates noted between different techniques in the clinical study were less than had been observed in earlier phantom-nodule detection studies. Possible reasons for these findings are discussed.

Clinical Trials as Topic↗
PubMed1992

Comparison of arousal responses to tracheal and face mask occlusions in sleeping newborn piglets.

The arousal responses after occlusion of the airway at the mid-trachea were compared with the responses after occlusion of the airway in a face mask in chronically instrumented 3- to 5-day-old piglets. For each site of occlusion arousal latency was significantly longer from active sleep than from quiet sleep. There was a significant increase in the frequency of early arousals after face mask occlusions compared with tracheal occlusions in both sleep states. During quiet sleep the frequency of arousal by 1 s after occlusion was 0.55 with face mask occlusions compared with 0.28 with tracheal occlusion (P less than 0.01). During active sleep the frequency of arousal by 3 s after a face mask occlusion was 0.32 compared with 0.08 after tracheal occlusion (P less than 0.05). Arousal from quiet sleep occurred before changes in arterial oxygen saturation. During active sleep mean saturation at arousal was not different between face mask and tracheal occlusions. Exposure of the upper airway to the pressures generated during airway occlusions results in earlier arousal in both quiet and active sleep, indicating a potential role for upper airway mechanoreceptors in initiating arousal in the newborn piglet.

Airway Obstruction↗
PubMed1989

Masking of circadian activity rhythms in canaries by light and dark.

Canaries (Serinus canaria) were kept singly in cages placed in an artificially illuminated, soundproof cabinet. Perch-hopping activity was recorded by means of a computer system. In three series of experiments, the activity rhythms of the birds were entrained to 24 hr by light-dark (LD) cycles with 4, 12, or 20 hr of light (L), respectively. The intensity of illumination was 10 lux in L and 0.25 lux in darkness (D). Under LD 4:20 and 12:12, the intensity of D was increased daily at the same zeitgeber time to 1 lux for 1 hr (L pulse) during about 8 consecutive days. This sequence was followed by 8 days without L pulses before giving another series of L pulses at a different zeitgeber time. Under LD 20:4, the intensity of L was decreased to 1 lux for 1 hr (D pulse). The activity of all birds was more or less increased by the L pulses (positive masking) and decreased by the D pulses (negative masking). The level of masking activity during the L and D pulses depended on the circadian phase at which the pulses were administered. Positive masking by L pulses was minimal about 5 hr after the beginning of D, and increased steadily thereafter. Negative masking by D pulses was maximal at the beginning and the end of L, and minimal during the middle.

Animals↗
PubMed2002

MASK, a large ankyrin repeat and KH domain-containing protein involved in Drosophila receptor tyrosine kinase signaling.

The receptor tyrosine kinases Sevenless (SEV) and the Epidermal growth factor receptor (EGFR) are required for the proper development of the Drosophila eye. The protein tyrosine phosphatase Corkscrew (CSW) is a common component of many RTK signaling pathways, and is required for signaling downstream of SEV and EGFR. In order to identify additional components of these signaling pathways, mutations that enhanced the phenotype of a dominant negative form of Corkscrew were isolated. This genetic screen identified the novel signaling molecule MASK, a large protein that contains two blocks of ankyrin repeats as well as a KH domain. MASK genetically interacts with known components of these RTK signaling pathways. In the developing eye imaginal disc, loss of MASK function generates phenotypes similar to those generated by loss of other components of the SEV and EGFR pathways. These phenotypes include compromised photoreceptor differentiation, cell survival and proliferation. Although MASK is localized predominantly in the cellular cytoplasm, it is not absolutely required for MAPK activation or nuclear translocation. Based on our results, we propose that MASK is a novel mediator of RTK signaling, and may act either downstream of MAPK or transduce signaling through a parallel branch of the RTK pathway.

Amino Acid Sequence↗
PubMed2004

Nonstoichiometric silica mask for fabricating reverse proton-exchanged waveguides in lithium niobate crystals.

Producing channel waveguides requires a photolithographic mask, but the standard technique of using thermally evaporated metal films for proton exchange has proved to be unsuitable for withstanding the rather aggressive process of reverse proton exchange. We report the fabrication of a nonstoichiometric silica mask by ion-plating plasma-assisted deposition. This mask is strong enough to resist both direct and reverse proton exchange and is also compatible with anisotropic dry etching for patterning the mask and with electric field poling. Our technique is a practical alternative to the use of SiO2 sputtered masks.

Journal Article↗
PubMed2006

Incorporating mask topography edge diffraction in photolithography simulations.

In deep ultraviolet lithography simulations, conventional application of Kirchhoff's boundary conditions on the mask surface provides the so-called "thin-mask" approximation of the object field. Current subwavelength lithographic operation, however, places a serious limitation on this approximation, which fails to account for the topographical, or "thick-mask," effects. In this paper, a new simulation model is proposed that is theoretically founded on the well-established physical theory of diffraction. This model relies on the key result that diffraction effects can be interpreted as an intrinsic edge property, and modeled with just two fixed parameters: width and transmission coefficient of a locally determined boundary layer applied to each chrome edge. The proposed model accurately accounts for thick-mask effects of the fields on the mask, greatly improving the accuracy of aerial image simulations in photolithography, while maintaining a reasonable computational cost.

Journal Article↗
PubMedDate not supplied

Hyperthermia-induced shedding and masking of melanoma-associated antigen.

Hyperthermia has been reported to induce a dose-dependent reduction in the expression of melanoma-associated surface antigens. The objective of the present work was to study the mechanisms for the reduction in the expression of the p250 antigen recognized by the monoclonal antibody 9.2.27. Measurements at 37 degrees C showed that antibody binding induced a certain degree of modulation (internalization) of the melanoma-associated antigen. Masking of the antigen due to internalization and/or damage in situ, as well as shedding of the antigen, were measured after hyperthermia, and found to increase in a heat-dose-dependent manner, although for antigen masked this increase was not significant compared with control cells at 37 degrees C. The sum of antigen shed and masked after hyperthermia correlated with the overall reduction in antigen expression measured independently. During hyperthermia, antigen was shed and masked in approximately equal amounts. After the treatment, hyperthermia-induced shedding continued as a function of time and caused a further reduction in antigen expression, but masking did not differ from 37 degrees C controls.

Antibodies, Monoclonal↗
PubMed1989

Masking in invertebrates.

Masking effects are a common feature of daily rhythmicity in invertebrates; and, particularly with respect to activity/rest cycles in arthropods and mollusks, there are numerous examples of masking in response to external environmental stimuli. Internal masking, in which endogenous processes modulate circadian patterns, has also been documented in a few species. In general, however, because of the absence of appropriate experimental investigations on masking, the functional significance (in an ecological sense) of masking effects is not understood.

Adaptation, Physiological↗
PubMed1989

Regression models for the estimation of circadian rhythms in the presence of effects due to masking.

The estimation of human circadian rhythms from experimental data is complicated by the presence of "masking" effects associated with the sleep-wake cycle. The observed rhythm may include a component due to masking, as well as the endogenous component linked to a circadian pacemaker. In situations where the relationship between the sleep-wake cycle and the circadian rhythm is not constant, it may be possible to obtain individual estimates of these two components, but methods commonly used for the estimation of circadian rhythms, such as the cosinor analysis, spectral analysis, average waveforms and complex demodulation, have not generally been adapted to identify the modulations that arise from masking. The estimates relate to the observed rhythms, and the amplitudes and acrophases do not necessarily refer to the endogenous rhythm. In this paper methods are discussed for the separation of circadian and masking effects using regression models that incorporate a sinusoidal circadian variation together with functions of time since sleep and time during sleep. The basic model can be extended to include a time-varying circadian rhythm and estimates are available for the amplitude and phase at a given time, together with their joint confidence intervals and tests for changes in amplitude and acrophase between any two selected times. Modifications of these procedures are discussed to allow for non-sinusoidal circadian rhythms, non-additivity of the circadian and time-since-sleep effects and the breakdown of the usual assumptions concerning the residual errors. This approach enables systematic masking effects associated with the sleep-wake cycle to be separated from the circadian rhythm, and it has applications to the analysis of data from experiments where the sleep-wake cycle is not synchronized with the circadian rhythm, for example after time-zone transitions or during irregular schedules of work and rest.

Circadian Rhythm↗