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At least 1,297 records · Page 72Linked to original sources
PubMed2005

Place of residence and distance to medical care influence the diagnosis of hepatitis C: a population-based study.

BACKGROUND/AIMS: In France, geographic access to medical care may affect the diagnosis of hepatitis C. The aims of this study were to compare the detection rates of hepatitis C in urban and rural areas after adjusting for distance to medical care, and evaluating the impact of the place of residence on patients' clinical characteristics. METHODS: Between 1994 and 2001, 1938 newly detected cases were recorded in a French population of 1,005,817 inhabitants. Age and sex-adjusted detection rates for 10(5) inhabitants were estimated for urban and rural areas and for classes of distance to the nearest practitioner. RESULTS: Detection rates were lower in rural than in urban areas [14.1, (95CI: 12.5-15.7) versus 24.7, (95CI: 23.5-26.0)] and decreased as the distance to the general practitioner increased [27.0, (95CI: 25.5-28.4) versus 13.7, (95CI: 12.1-15.3) for a cutoff value of 1.5 km]. In multivariate analyses, detection rates were only influenced by the distance to general practitioner. Hepatocellular carcinoma at diagnosis was more frequent among rural than among urban patients (adjusted OR = 2.28, 95CI: 0.97-5.39, P = 0.059). CONCLUSIONS: A poorer geographic access to care explained the lower detection of hepatitis C in rural areas. Hepatocellular carcinoma was more frequent in rural patients. It may result from later detection and/or involvement of environmental factors on hepatocarcinogenesis.

Adult↗
PubMed2004

2H[19F] REDOR for distance measurements in biological solids using a double resonance spectrometer.

A new approach for distance measurements in biological solids employing 2H[19F] rotational echo double resonance was developed and validated on 2H,19F-D-alanine and an imidazopyridine based inhibitor of the gastric H+/K+-ATPase. The 2H-19F double resonance experiments presented here were performed without 1H decoupling using a double resonance NMR spectrometer. In this way, it was possible to benefit from the relatively longer distance range of fluorine without the need of specialized fluorine equipment. A distance of 2.5 +/- 0.3 A was measured in the alanine derivative, indicating a gauche conformation of the two labels. In the case of the imidazopyridine compound a lower distance limit of 5.2 A was determined and is in agreement with an extended conformation of the inhibitor. Several REDOR variants were compared, and their advantages and limitations discussed. Composite fluorine dephasing pulses were found to enhance the frequency bandwidth significantly, and to reduce the dependence of the performance of the experiment on the exact choice of the transmitter frequency.

Alanine↗
PubMed2005

Sensitivity of surface EMG-based conduction velocity estimates to local tissue in-homogeneities--influence of the number of channels and inter-channel distance.

The aim of this simulation study was to investigate the influence of local tissue in-homogeneities on the estimates of muscle fiber conduction velocity (CV) from surface EMG signals. A recently developed analytical surface EMG model was used to generate simulated surface EMG signals from a planar layered volume conductor, comprised of the muscle tissue and fat layer, with spheres (1 mm radius) in the fat layer of conductivity different from the surrounding tissue. CV was estimated with a maximum likelihood multi-channel approach, varying the number of channels and the inter-channel distance used for the estimate. The action potentials detected along the muscle fiber direction changed shape due to the presence of the in-homogeneities, thus affecting CV estimates. CV estimates were influenced by the location of the in-homogeneities with respect to the fiber and detection electrodes. The maximum percent variation of CV estimates due to the presence of in-homogeneities decreased with increasing number of channels and inter-channel distance: 19.6% (2 channels), 12.1% (3 channels), 6.4% (4 channels), for 5 mm inter-channel distance, and 12.0% (2 channels), 5.2% (3 channels), 2.4% (4 channels), for 10 mm inter-channel distance (for double differential detection). The results were in agreement and explained previous experimental findings. It was concluded that multi-channel methods for CV estimation significantly reduce the sensitivity of CV estimates to tissue in-homogeneities.

Action Potentials↗
PubMed2006

Comparison of global positioning and computer-based tracking systems for measuring player movement distance during Australian football.

Sports scientists require a thorough understanding of the energy demands of sports and physical activities so that optimal training strategies and game simulations can be constructed. A range of techniques has been used to both directly assess and estimate the physiological and biochemical changes during competition. A fundamental approach to understanding the contribution of the energy systems in physical activity has involved the use of time-motion studies. A number of tools have been used from simple pen and paper methods, the use of video recordings, to sophisticated electronic tracking devices. Depending on the sport, there may be difficulties in using electronic tracking devices because of concerns of player safety. This paper assesses two methods currently used to measure player movement patterns during competition: (1) global positioning technology (GPS) and (2) a computer-based tracking (CBT) system that relies on a calibrated miniaturised playing field and mechanical movements of the tracker. A range of ways was used to determine the validity and reliability of these methods for tracking Australian footballers for distance covered during games. Comparisons were also made between these methods. The results indicate distances measured using CBT overestimated the actual values (measured with a calibrated trundle wheel) by an average of about 5.8%. The GPS system overestimated the actual values by about 4.8%. Distances measured using CBT in experienced hands were as accurate as the GPS technology. Both systems showed relatively small errors in true distances.

Australia↗
PubMed2004

A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance.

We present in this paper a picture of the neural systems controlling defense that updates and simplifies Gray's "Neuropsychology of Anxiety". It is based on two behavioural dimensions: 'defensive distance' as defined by the Blanchards and 'defensive direction'. Defensive direction is a categorical dimension with avoidance of threat corresponding to fear and approach to threat corresponding to anxiety. These two psychological dimensions are mapped to underlying neural dimensions. Defensive distance is mapped to neural level, with the shortest defensive distances involving the lowest neural level (periaqueductal grey) and the largest defensive distances the highest neural level (prefrontal cortex). Defensive direction is mapped to separate parallel streams that run across these levels. A significant departure from prior models is the proposal that both fear and anxiety are represented at all levels. The theory is presented in a simplified form that does not incorporate the interactions that must occur between non-adjacent levels of the system. It also requires expansion to include the dimension of escapability of threat. Our current development and these proposed future extensions do not change the core concepts originally proposed by Gray and, we argue, demonstrate their enduring value.

Amygdala↗
PubMed2005

Global shape recognition is modulated by the spatial distance of local elements--evidence from simultanagnosia.

Simultanagnosia is a rare deficit that impairs individuals in perceiving several objects at the same time. It is usually observed following bilateral parieto-occipital brain damage. Despite the restrictions in perceiving the global aspect of a scene, processing of individual objects remains unaffected. The mechanisms underlying simultanagnosia are not well understood. Previous findings indicated that the integration of multiple objects into a holistic representation of the environment is not impossible per se, but might depend on the spatial relationship between individual objects. The present study examined the influence of inter-element distances between individual objects on the recognition of global shapes in two patients with simultanagnosia. We presented Navon hierarchical letter stimuli with different inter-element distances between letters at the Local Scale. Improved recognition at the Global Scale was observed in both patients by reducing the inter-element distance. Global shape recognition in simultanagnosia thus seems to be modulated by the spatial distance of local elements and does not appear to be an all-or-nothing phenomenon depending on spatial continuity. The findings seem to argue against a deficit in visual working memory capacity as the primary deficit in simultanagnosia. However, further research is necessary to investigate alternative interpretations.

Agnosia↗
PubMed2006

Costs of refractive correction of distance vision impairment in the United States, 1999-2002.

OBJECTIVE: Correctable vision impairment caused by refractive error is common in the United States population. We estimated the direct costs of providing eyeglasses to all Americans (age> or =12) who need refractive correction to achieve good distance vision. DESIGN: Cross-sectional study of a nationally representative sample of United States citizens. PARTICIPANTS: Participants in the 1999-2002 National Health and Nutrition Examination Survey (NHANES), age > or = 12 years. The NHANES examines a nationally representative sample of the U.S. noninstitutionalized, civilian population. METHODS: Presenting and corrected visual acuity data were obtained using an autorefractor from 13,211 (93.0%) of the 14,203 participants who visited the NHANES Mobile Examination Center in 1999 through 2002. Need for refractive correction was defined by current use of corrective lenses for distance vision, improvement to good visual acuity following autorefractor correction (using several cutpoints to define good visual acuity), or both. MAIN OUTCOME MEASURES: Estimates of direct cost for refractive correction (1 pair of complete eyeglasses and a refraction examination) were computed based on Centers for Medicare & Medicaid Services fee schedules for 2000 and also based on expenditure data from the Medical Expenditure Panel Survey. RESULTS: The NHANES results indicate that >110 million Americans could or do achieve normal vision with refractive correction. The annual direct cost of correcting distance vision impairment is at least $3.8 billion. Of this amount, $780 million represents the annual cost of providing distance vision correction for persons > age 65. CONCLUSIONS: Correctable vision impairment due to refractive error is common in the United States population. These cost estimates provide useful information for public health endeavors aimed at provision of refractive correction to those who need it.

Adolescent↗
PubMed2004

Tip-to-sample distance dependence of an electrostatic force in KFM measurements.

In most scanning probe methods like an atomic force microscopy, a cantilever is mechanically vibrated in order to obtain topographies. Therefore, a tip-to-sample distance periodically changes during the scanning. Since the electrostatic force, which is a long-range force, is used for potential feedback in Kelvin probe force microscopy (KFM), such mechanical vibration leads to the fluctuation of the electrostatic force between the tip and the sample. In this study, firstly, we performed two-dimensional simulations of the electric fields between surfaces of the tip and the sample and evaluated the tip-to-sample distance dependence of the electrostatic force. Secondly, we experimentally confirmed the existence of the fluctuation of the electrostatic force and the tip-to-sample distance dependence of the electrostatic force was evaluated. Both the simulations and the experiments on the tip-to-sample distance dependence showed the importance of considering the tip sidewall effect in the KFM potential determination.

Journal Article↗
PubMed2005

Comparison of extended field of view and dual image ultrasound techniques: accuracy and reliability of distance measurements in phantom study.

This study was undertaken to investigate and compare the accuracy and reliability of dual image and extended field-of-view (EFOV) ultrasound (US) techniques in distance measurements using acoustic phantoms. Ten tissue phantoms were constructed and were scanned twice with an interval of 3 days by two operators. Measurements of various known distance (ranging from 4.6 to 7.2 cm) in the phantoms were made with dual image and EFOV US. Results showed that both dual image and EFOV US have a high accuracy and reliability in distance measurements, with the EFOV US (r = 0.997 to 0.998, reproducibility = 99.8%, repeatability = 98.2 to 99.8%) being slightly more accurate and reliable than dual image US (r = 0.948 to 0.981, reproducibility = 94.6%, repeatability = 89.6 to 97.9%). EFOV US has a higher accuracy and reliability than dual image US in distance measurements. However, the dual image US is a useful alternative with a high accuracy and reliability when EFOV US is not available.

Data Display↗
PubMed2003

Is there a prognostic difference between depth of myometrial invasion and the tumor-free distance from the uterine serosa in endometrial cancer?

OBJECTIVE: The objective was to determine whether tumor-free distance from the uterine serosa is more predictive of patient outcome than depth of endometrial cancer invasion into the myometrium. METHODS: Patients with surgically staged endometrial adenocarcinoma between 1997 and 2000 were identified. Depth of myometrial invasion (DOI) was identified defined as the distance between endometrial-myometrial junction and deepest myometrial invasion. Tumor-free distance from the uterine serosa (TFD) was defined as the distance between the serosa and deepest myometrial invasion. DOI and TFD were expressed as continuous variables and compared with traditional surgicopathologic variables, recurrence, and survival to determine their predictive and prognostic significance. RESULTS: We identified 153 patients who met study criteria. The median DOI was 0.5 cm and the median TFD was 1.4 cm. The most common stage was IB, and 23 patients had positive nodes. With a median follow-up of 29 months, 10 patients have recurred. When DOI and TFD were compared in a univariate model, TFD was an equal or more significant predictor of traditional surgicopathologic variables. TFD but not DOI was predictive of recurrence. Likewise, TFD was a more significant predictor of dying from disease than DOI. In a multivariate model, TFD was shown to correlate with surgicopathologic variables, recurrence risk, and survival. DOI, however, was not predictive unless myometrial thickness was included in the model. A TFD of 1 cm maximized the balance of sensitivity and specificity in predicting recurrence. CONCLUSION: TFD as a single measurement carries significant prognostic importance in women with comprehensively staged endometrial cancer.

Adult↗
PubMed2006

Margin distance and other clinico-pathologic prognostic factors in vulvar carcinoma: a multivariate analysis.

OBJECTIVES: To determine the importance of margin status and other prognostic factors associated with the recurrence and survival of patients with squamous cell vulvar carcinoma. METHODS: Data were analyzed using Kaplan-Meier methods and Cox proportional hazards regression. All slides were re-reviewed by two gynecologic pathologists. RESULTS: Ninety patients (median age: 69) were treated for vulvar carcinoma from 1984 to 2002, including 28 FIGO stage I, 20 stage II, 26 stage III and 16 with stage IV disease. Sixty-three (70%) patients underwent complete radical vulvectomies and 27 (30%) had modified radical vulvectomies. Nineteen (20%) patients received adjuvant radiotherapy. Five-year disease-specific survival rates were 100%, 100%, 86% and 29% for stages I-IV, respectively. None of the 30 patients with a pathologic margin distance >8 mm had local recurrence. Of the 53 women with tumor-free pathologic margin of <8 mm, 12 (23%) had a local recurrence. Moreover, women with >2 positive groin nodes had significantly higher recurrence risk compared to those with <2 metastatic groin nodes (p<0.001). On multivariate analysis, positive groin nodes and margin distance were important prognostic factors for recurrence. Moreover, stage, tumor size, margin distance, and depth of invasion were significant independent predictors for disease-specific survival. The median follow-up was 58 months (range: 2-188). CONCLUSIONS: Pathologic margin distance is an important predictor of local vulvar recurrence. Our data suggest that a > or =8-mm pathologic margin clearance leads to a high rate of loco-regional control.

Adult↗
PubMed2002

Contribution of vergence adaptation to difference in vertical deviation between distance and near viewing in patients with superior oblique palsy.

PURPOSE: To evaluate the adaptive vertical vergence aftereffect and determine whether it contributes to a difference of vertical deviation with respect to gaze distance in patients with vertical strabismus. DESIGN: Prospective noncomparative studies. METHODS: Eighty-four patients with unilateral superior oblique palsies were enrolled and classified into three types-A, B, and C-based on the difference in vertical deviation between distant and near viewing. The prism adaptation test was performed for 2 to 3 hours to correct vertical deviation and the response of vertical deviation to the prism adaptation test was compared among the three types RESULTS: Adaptive vertical vergence aftereffect, defined as an increase of deviation by 5 prism diopters or more with the prism adaptation test, was identified in 13 patients (16%) at distance and in 23 patients (27%) at near viewing. Among the three types, the adaptive vergence aftereffect contributed mostly to the type B, in which distance deviation exceeds near deviation. Nine patients (39%) of type B changed to type A category with the prism adaptation test; and of these, 7 increased near deviation so that the deviation difference between distant and near viewing decreased. CONCLUSION: The adaptive vertical vergence aftereffect contributes to a difference in vertical deviation between distant and near viewing. The vertical prism adaptation test is specifically useful to determine the extent of surgery by breaking fusional vergence in patients with hypertropia in whom deviation differs with respect to viewing distance.

Adaptation, Ocular↗
PubMed1997

A distance measurement between specific sites on the cytoplasmic surface of bovine rhodopsin in rod outer segment disk membranes.

Structural information on mammalian integral membrane proteins is scarce. As part of work on an alternative approach to the structure of bovine rhodopsin, a method was devised to obtain an intramolecular distance between two specific sites on rhodopsin while in the rod outer segment disk membrane. In this report, the distance between the rhodopsin kinase phosphorylation site(s) on the carboxyl terminal and the top of the third transmembrane helix was measured on native rhodopsin. Rhodopsin was labeled with a nuclear spin label (31P) by limited phosphorylation with rhodopsin kinase. Major phosphorylation occurs at serines 343 and 338 on the carboxyl terminal. The phosphorylated rhodopsin was then specifically labeled on cysteine 140 with an electron spin label. Magic angle spinning 31P-nuclear magnetic resonance revealed the resonance arising from the phosphorylated protein. The enhancement of the transverse relaxation of this resonance by the paramagnetic spin label was observed. The strength of this perturbation was used to determine the through-space distance between the phosphorylation site(s) and the spin label position. A distance of 18 +/- 3 A was obtained.

Animals↗
PubMed2001

Comparison of electron paramagnetic resonance methods to determine distances between spin labels on human carbonic anhydrase II.

Four doubly spin-labeled variants of human carbonic anhydrase II and corresponding singly labeled variants were prepared by site-directed spin labeling. The distances between the spin labels were obtained from continuous-wave electron paramagnetic resonance spectra by analysis of the relative intensity of the half-field transition, Fourier deconvolution of line-shape broadening, and computer simulation of line-shape changes. Distances also were determined by four-pulse double electron-electron resonance. For each variant, at least two methods were applicable and reasonable agreement between methods was obtained. Distances ranged from 7 to 24 A. The doubly spin-labeled samples contained some singly labeled protein due to incomplete labeling. The sensitivity of each of the distance determination methods to the non-interacting component was compared.

Carbonic Anhydrases↗
PubMed2004

Interresidual distance determination by four-pulse double electron-electron resonance in an integral membrane protein: the Na+/proline transporter PutP of Escherichia coli.

Proximity relationships within three doubly spin-labeled variants of the Na+/proline transporter PutP of Escherichia coli were studied by means of four-pulse double electron-electron resonance spectroscopy. The large value of 4.8 nm for the interspin distance determined between positions 107 in loop 4 and 223 in loop 7 strongly supports the idea of these positions being located on opposite sides of the membrane. Significant smaller values of between 1.8 and 2.5 nm were found for the average interspin distances between spin labels attached to the cytoplasmic loops 2 and 4 (position 37 and 107) and loops 2 and 6 (position 37 and 187). The large distance distribution widths visible in the pair correlation functions reveal a high flexibility of the studied loop regions. An increase of the distance between positions 37 and 187 upon Na+ binding suggests ligand-induced structural alterations of PutP. The results demonstrate that four-pulse double electron-electron resonance spectroscopy is a powerful means to investigate the structure and conformational changes of integral membrane proteins reconstituted in proteoliposomes.

Amino Acid Transport Systems, Neutral↗
PubMed1989

Lateral diffusion in an archipelago. Distance dependence of the diffusion coefficient.

An understanding of the distance dependence of the lateral diffusion coefficient is useful in comparing the results of diffusion measurements made over different length scales, and in analyzing the kinetics of mobile redox carriers in organelles. A distance-dependent, concentration-dependent diffusion coefficient is defined, and it is evaluated by Monte Carlo calculations of a random walk by mobile point tracers in the presence of immobile obstacles on a triangular lattice, representing the diffusion of a lipid or a small protein in the presence of immobile membrane proteins. This work confirms and extends the milling crowd model of Eisinger, J., J. Flores, and W. P. Petersen (1986. Biophys J. 49:987-1001). Similar calculations for diffusion of mobile particles interacting by a hard-core repulsion yield the distance dependence of the self-diffusion coefficient. An expression for the range of short-range diffusion is obtained, and the distance scales for various diffusion measurements are summarized.

Diffusion↗
PubMed1989

Simultaneous determination of intramolecular distance distributions and conformational dynamics by global analysis of energy transfer measurements.

Fluorescence energy transfer is widely used for determination of intramolecular distances in macromolecules. The time dependence of the rate of energy transfer is a function of the donor/acceptor distance distribution and fluctuations between the various conformations which may occur during the lifetime of the excited state. Previous attempts to recover both distance distributions and segmental diffusion from time-resolved experiments have been unsuccessful due to the extreme correlation between fitting parameters. A method has been developed, based on global analysis of both donor and acceptor fluorescence decay curves, which overcomes this extreme cross-correlation and allows the parameters of the equilibrium distance distributions and intramolecular diffusion constants to be recovered with high statistical significance and accuracy. Simulation studies of typical intramolecular energy transfer experiments reveal that both static and dynamic conformational distribution information can thus be obtained at a single temperature and viscosity.

Biopolymers↗
PubMed1991

On the relationship between distance information derived from cross-linking and from resonance energy transfer, with specific reference to sites located on myosin heads.

The techniques of fluorescence resonance energy transfer (FRET) and cross-linking can provide complementary information concerning the relative separation of a pair of sites. Cross-linking experiments provide an assessment of the distance of closest approach between a pair of sites. FRET measurements, by contrast, yield information about the average distance between the pair of sites. We have taken advantage of hybrid myosins to understand the relationship between distances obtained for a pair of equivalent sites, one on each myosin head, using both FRET (steady-state and time-decay) and cross-linking techniques. The rigid cross-linker, 4-4'-dimaleimidyl-stilbene-2-2'-disulfonic acid (DMSDS), can efficiently cross-link the two myosin regulatory light-chains, each at residue Cys50 of the Mercenaria regulatory light chain (Chantler, P.D., and S. M. Bower. 1988. J. Biol. Chem. 263:938-944), indicating that these sites can come within 18 +/- 2 A of each other. In a complementary set of experiments, steady-state and time-decay measurements using fluorescence donor/acceptor pairs located at these same sites indicate transfer efficiencies of somewhat less than 20%, suggesting an average separation of greater than 50 A between sites (Chantler, P. D., and T. Tao. 1986. J. Mol. Biol. 192:87-99). Here, we present theoretical calculations which show that efficient cross-linking can be achieved readily in dynamic systems such as the heads of myosin, even though the necessary subpopulation of proximate molecules at any instant may be below the detection limits of time-decay-FRET. Therefore, cross-linking experiments can provide important ancillary information about the extent of motions within a marcomolecular system when used in conjunction with FRET.As a corollary, demonstration of extensive cross-linking does not necessarily indicate a static proximity; the mean separation distance should be ascertained by other methods such as FRET.

Binding Sites↗