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Results for “reflection”

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PubMed1986

Foveal cone pigment density difference and reflectance in retinitis pigmentosa.

Cone pigment density difference refers to a change in light absorption by cones before and after bleaching of their visual pigments. With a television ophthalmoscope image processor, we measured the foveal cone pigment density difference in patients with retinitis pigmentosa (RP), good central vision, and no clinically apparent foveal lesion. Foveal reflectance was obtained at 12 different wavelengths of illumination. Compared with similar-aged normal subjects, most patients with dominantly inherited RP had normal or minimally reduced cone pigment density difference within the central fovea, relatively lower than normal density difference at the foveal margin, and increased foveal reflectance. Compared with these normal subjects, patients with recessively inherited RP had significantly reduced cone pigment density difference within the central fovea, relatively more normal density difference at the foveal margin, and normal foveal reflectance.

Absorption↗

PubMed1993

Reflectance feedback control of photocoagulation in vivo.

OBJECTIVE: The objective of this research was to build a real-time feedback system that controlled lesion size. Two-dimensional reflectance images were acquired with a charge-coupled device camera during irradiation, and argon laser exposure was ended when parameters of the image reached prespecified values. METHODS: The real-time feedback control system was tested by creating lesions at different power levels in pigmented rabbits. Laser exposure time was controlled by monitoring the central reflectance. RESULTS: Results of feedback-controlled lesions formed in vivo in pigmented rabbits are presented. An ability to produce uniform lesions despite variation in tissue absorption or changes in laser power is demonstrated. CONCLUSIONS: Reflectance control of photocoagulation is possible; incorporation of feedback during photocoagulation has numerous therapeutic and safety benefits over current ballistic delivery.

Animals↗

PubMed2000

Comparison of narrow-band reflectance spectroscopy and tristimulus colorimetry for measurements of skin and hair color in persons of different biological ancestry.

We have used two modern computerized handheld reflectometers, the Photovolt ColorWalk colorimeter (a tristimulus colorimeter; Photovolt, UMM Electronics, Indianapolis, IN) and the DermaSpectrometer (a specialized narrow-band reflectometer; Cortex Technology, Hadsund, Denmark), to compare two methods for the objective determination of skin and hair color. These instruments both determine color by measuring the intensity of reflected light of particular wavelengths. The Photovolt ColorWalk instrument does so by shining a white light and sensing the intensity of the reflected light with a linear photodiode array. The ColorWalk results can then be expressed in terms of several standard color systems, most importantly, the Commission International d'Eclairage (CIE) Lab system, in which any color can be described by three values: L*, the lightness; a*, the amount of green or red; and b*, the amount of yellow or blue. Instead of a white light and photodiodes, the DermaSpectrometer uses two light-emitting diodes (LEDs), one green and one red, to illuminate a surface, and then it records the intensity of the reflected light. The results of these readings are expressed in terms of erythema (E) and melanin (M) indices. We measured the unexposed skin of the inner upper arm, the exposed skin of the forehead, and the hair, of 80 persons using these two instruments. Since it is important for the application of these measures in anthropology that we understand their relationship across a number of different pigmentation levels, we sampled persons from several different groups, namely, European Americans (n = 55), African Americans (n = 9), South Asians (n = 7), and East Asians (n = 9). In these subjects, there is a very high correlation between L* and the M index for the inner arm (R(2) = 0.928, P < 0.001), the forehead (R(2) = 0.822, P < 0.001), and the hair (R(2) = 0.827, P < 0.001). The relationship between a* and the E index is complex and dependent on the pigmentation level. We conclude that while both types of instruments provide accurate estimates of pigment level in skin and hair, measurements using narrow-band instruments may be less affected by the greater redness of certain body sites due to increased vascularization.

Adult↗

PubMed2000

New high-DQE imaging plate scanner using the reflected readout laser signal for noise corrections.

Imaging Plates (IPs) are in principle ideal electron detectors combining a large active layer area with a high sensitivity, linear dynamic range detection over 5 orders of magnitude. A moderate resolution and a decreasing detection quantum efficiency (DQE) for higher electron doses limit their use so far. The decrease of the DQE results from linear noise contributed by readout laser instabilities and inhomogeneities of the IP active layer. Here we present data on a new IP drum scanner prototype. This scanner combines twin channel amplification electronics with a new type of readout laser which allows a smaller readout focus and increased stability. The current nominal pixel size is 25 microm, and the measured modulation transfer function (MTF) indicates that further reduction of the scanning step size down to pixel sizes in the range of 12-15 microm should be possible. A unique feature of the new scanner is the simultaneous recording of the reflected readout laser light. The reflected light signal can be used for a posteriori alignment of repeated scans of one individual IP and for a correction of one part of the high spatial frequency noise contribution (reflected light correction). The posteriori alignment now allows an easy conventional gain normalization of the luminescence signal without using special markers on the IP. Both corrections lead to an increase of the DQE for high electron doses.

Biophysical Phenomena↗

PubMed1999

Serum interleukin-6 level reflects the tumor proliferative activity in patients with colorectal carcinoma.

BACKGROUND: Interleukin (IL)-6 plays a central role as a differentiation and growth factor of tumor cells. It may be hypothesized that increased serum IL-6 derives from the tumor tissue, and that serum IL-6 levels consequently reflect the biologic characteristics of the tumor. The authors investigated the association between the serum levels of IL-6 in colorectal carcinoma patients and the biologic characteristics of the tumor as well as clinicopathologic status of the patients. METHODS: Serum and tissue levels of IL-6 in 70 patients were determined using an immunoradiometric assay. Expression of IL-6 and IL-6 receptor were evaluated immunohistochemically. The proliferative activity of the tumor was assessed by nuclear Ki-67 labeling index. RESULTS: The concentration of serum IL-6 in the patients was significantly higher than that in normal controls. The tissue concentration of IL-6 in tumor tissue was significantly higher than that in normal mucosa, and was correlated strongly with the serum IL-6 concentration. The serum IL-6 concentration was correlated with clinicopathologic parameters, including liver metastases and tumor size, and with proliferative activity of the tumor as assessed by the Ki-67 labeling index. In the patients with Stage I or II tumors, the preoperative serum IL-6 concentration was reduced significantly 3 months after surgery. Immunohistochemically, tumor tissues that expressed IL-6 immunoreactivity had a higher incidence of expression of IL-6 receptor immunoreactivity. CONCLUSIONS. Serum IL-6 concentration reflects IL-6 concentration in the tumor component and may reflect the proliferative activity of the tumor in patients with colorectal carcinoma.

Adult↗

PubMed1999

A high resolving power multiple reflection matrix-assisted laser desorption/ionization time-of-flight mass spectrometer.

Two electrostatic mirrors, mounted symmetrically on the same optical axis facing each other, are used to increase the time-of-flight of molecular ions produced in matrix-assisted laser desorption/ionization (MALDI). The mirrors, which are used in the non-compensating mode, are located between a MALDI ion source and a stop detector. The source is operated at 10.5 kV acceleration voltage using the delayed extraction technique. The high voltage for the mirror arrangement is switched on after the desorption event when the molecular ions have drifted into the region between the mirrors. The ions are trapped by successive reflections of the opposite electrostatic fields in the mirrors until the electric fields are switched off. The number of reflections depends on the speed of the ions when they enter the mirror trap and the ontime of the mirrors. When the electric fields are removed during the motion of the ions towards the stop detector, the ions penetrate the grids of the mirror and reach that detector. The extension of the flight path due to the number of reflections is used to increase the resolving power in time-of-flight spectra. Values of 55,000 for substance-P (MW 1346.7) and 31,000 for bovine insulin (MW 5734) were obtained for single laser shot spectra.

Algorithms↗

PubMed2006

Information-seeking behaviors and reflective practice.

INTRODUCTION: As they care for patients, physicians raise questions, but they pursue only a portion of them. Without the best information and evidence, care and patient safety may be compromised. Understanding when and why problems prompt physicians to look for information and integrate results into their knowledge base is critical and shapes one part of reflection about care. This study explores the role of the Internet in gathering medical information as one step in that reflective practice, the barriers to its use, and changes in utilization over time. METHODS: A questionnaire with 18 items adapted from previous studies was sent by facsimile to a randomly selected sample of U.S. physicians in all specialties and active in practice. RESULTS: Specific patient problems and latest research in a specific topic most often prompt physicians to search on the Internet. Younger physicians and female physicians were most likely to seek information on a specific patient problem. Only 9% of all respondents (n = 2,500) searched for information during a patient encounter. When unsure about diagnostic and management issues for a complex case, 41.3% chose to consult with a colleague or read from a text (22.8%). Searching most often occurred at home after work (38.2%) or during breaks in the day (35.7%). Most (68.7%) found the information they were looking for more than 51% of the time. Searching was facilitated by knowing preferred sites and access in the clinical setting. The greatest barriers to answering clinical questions included a lack of specific information and too much information to scan. DISCUSSION: Although physicians are increasingly successful and confident in their Internet searching to answer questions raised in patient care, few choose to seek medical information during a patient encounter. Internet information access may facilitate overall reflection on practice; physicians do not yet use this access in a just-in-time manner for immediately solving difficult patient problems but instead continue to rely on consultation with colleagues. Professional association Web sites and point-of-care databases are helpful. From physicians' use of the Internet, professionals in continuing medical education must learn which search engines and sites are trusted and preferred.

Attitude of Health Personnel↗

PubMed2003

Abnormal cerebellar histogenesis in PEX2 Zellweger mice reflects multiple neuronal defects induced by peroxisome deficiency.

The form and circuitry of the cerebellum develops by a complex process that requires integration of afferent-target interactions between multiple neuronal populations and migratory patterns established by neuron-glial interactions. Analysis of mice lacking the PEX2 peroxisome assembly gene, in which peroxisomal function is disrupted, reveals abnormal cerebellar histogenesis due to the disturbance of multiple cellular processes within neurons. Defects in cerebellar growth and the rostro-caudal foliation pattern reflect a reduced granule neuron population and abnormal Purkinje cell dendrite development. In granule neurons, there is increased apoptotic cell death and delayed movement from the EGL to IGL that reflects cell cycle, maturational and migrational abnormalities. The underlying Purkinje cells have stunted dendrite arbors with abnormal branching patterns, which may reflect altered inductive influences from the delayed granule neuron translocation. A delayed arborization of mutant olivary climbing fibers and their defective translocation from the perisomatic to the dendritic compartment of Purkinje cells results in numerous spines on the soma and proximal dendrites of Purkinje cells. Distal Purkinje cell dendritic spines also display abnormal morphology. These Purkinje cell dendritic abnormalities are seen in association with persistent and enlarged axonal spheroids, further indicating the presence of a degenerative process within the Purkinje cell. This PEX2(-/-) mouse model for the human peroxisomal biogenesis disorder Zellweger syndrome illustrates the complex interplay of abnormal developmental processes in the cerebellum and the importance of peroxisomal function for neuronal migration, proliferation, differentiation, and survival.

Aging↗

PubMed2004

Phenotypic classification of human CD8+ T cells reflecting their function: inverse correlation between quantitative expression of CD27 and cytotoxic effector function.

Phenotypic classification of human CD8(+) T cells using three cell surface markers, CD27, CD28 and CD45RA, was recently suggested to be useful for identification of naive, memory and effector CD8(+) T cells. However, it still remains unclear whether such classification precisely reflects functional classification of CD8(+) T cells. To clarify this, we characterized each CD27CD28CD45RA subset of total and human cytomegalovirus (HCMV)-specific CD8(+) T cells by analyzing the expression of perforin and two chemokine receptors, CCR5 and CCR7, as well as their function. An inverse correlation between perforin and CD27 expression was found in all four CD28CD45RA subsets. Therefore, to achieve a phenotypic classification of CD8(+) T cells that more precisely reflects their function, the CD27(+) subset was divided into CD27(low) and CD27(high) subsets based on the expression level of CD27. Functional and flow cytometric analyses of CD27CD28CD45RA subsets showed that this phenotypic classification reflects functional classification of CD8(+) T cells. HCMV-specific CD8(+) T cells from healthy HCMV-seropositive individuals were predominantly found in effector and memory/effector subsets, indicating that HCMV-specific effector CD8(+) T cells are actively induced by HCMV replication in healthy HCMV carriers. Phenotypic analyses of CD8(+) T cells using this classification will enable the characterization of antigen-specific CD8(+) T cells.

CD28 Antigens↗

PubMedDate not supplied

Assessment of pepper spray product potency in Asian and Caucasian forearm skin using transepidermal water loss, skin temperature and reflectance colorimetry.

Historically, pepper spray product potency has been established using a taste test evaluation. A taste test is subjective and may not be appropriate for assessing pepper potency in skin. The current study evaluated chemically diverse pepper sprays in human forearm skin using three objective, noninvasive parameters: transepidermal water loss, skin surface temperature and erythema, as a means for assessing dermal pharmacology, toxicology and product potency. Five commercial pepper spray products containing various capsaicinoid analogs at various concentrations were evaluated in duplicate on volar forearms of six Caucasians and six Asians using a 10 min exposure. Mean surface skin temperature, transepidermal water loss results were highly variable and therefore did not demonstrate dose responsive behavior to increasing capsaicinoid concentrations. Erythema, as measured by increases in a* (reflected light in the red-to-green color spectrum) of the L*a*b* uniform color scale, was superior among parameters evaluated in discriminating pepper spray potency and correlated well with the relative and total capsaicinoid concentration in the products. Products containing greater than 16 mg ml(-1) capsaicinoid concentration produced greater erythema responses in Caucasians than Asians. Asians responded greater to the synthetic analog, nonivamide, than to mixtures of capsaicinoids, while Caucasians responded equally to both capsaicinoid analogs. Thus, pepper spray product potency in human skin reflects the total capsaicinoid concentration, the specific capsaicin analog(s) present, and the race of the individual exposed. The finding that the reflectance colorimeter a* scale can differentiate these parameters in skin will have a significant impact on evaluating the use and efficacy of pepper spray products in humans.

Adult↗

PubMed1991

Assessment by reflection ultrasound method of the effect of intermittent slow-release sodium fluoride-calcium citrate therapy on material strength of bone.

It has been suggested that fluoride therapy, while increasing bone mass, produces bone with inferior mechanical properties. In the present report this hypothesis was tested using a novel reflection ultrasound technique. Transiliac crest bone biopsies were obtained from 16 patients with osteoporosis and vertebral compression fractures (12 women and 4 men, mean age 56 years) before and after approximately 2 years of intermittent slow-release sodium fluoride therapy (25 mg twice a day) combined with continuous calcium citrate supplementation. Samples were analyzed by a reflection ultrasound method, which analyzes ultrasound velocity with a sample site resolution of 200 microns and thus provides a measure of the mechanical property of single trabeculae (material). For the group, mean fractional change in velocity increased 6.1 +/- 2.3% (SEM) from a mean value of 3303 +/- 80 to 3484 +/- 55 m/s (p = 0.028). A total of 13 patients (81%) demonstrated higher velocities after treatment. Thus reflection ultrasound analysis of bone appears to provide a sensitive means of assessing changes in the material property of bone. Furthermore, these results suggest that the treatment regimen utilized in these patients improves strength of bone at the material or trabecular level largely independently of change in bone mass. The combination therapy also increased spinal (L2-L4) bone density for the group as assessed by dual-photon absorptiometry (5.3 +/- 2.0%). There was no significant correlation between the change in ultrasound velocity and bone density (r = 0.0026, p = 0.996).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2004

Characterization of port wine stain skin erythema and melanin content using cross-polarized diffuse reflectance imaging.

BACKGROUND AND OBJECTIVES: Objective methods to assess quantitatively port wine stain (PWS) blanching in response to laser therapy are needed to improve laser therapeutic outcome. Previous studies have attempted to assess objectively PWS color based on point measurement devices. To date, these approaches have typically been limited by a number of factors such as small test area and need for contact. To address these issues, a cross-polarized diffuse reflectance imaging system and color image analysis method has been developed to evaluate quantitatively erythema and melanin content in PWS skin. STUDY DESIGN/MATERIALS AND METHODS: A cross-polarized diffuse reflectance system has been constructed to acquire high resolution digital images while minimizing artifacts such as glare, shadowing, and nonuniform illumination effects that can compromise image fidelity. Furthermore, an image analysis algorithm has also been developed to analyze normal and PWS skin in terms of CIEL*a*b* color space parameters. Using the algorithm, images of color space intensity, L*, and saturation, a*, indices have been calculated to extract quantitative metrics of melanin and erythema, respectively. RESULTS: Compared to the cross-polarized diffuse reflectance image, the a* index image enhanced the contrast in regions of high and low erythema and seems to have quasi correlation with the L* index image. In the presented PWS patient example, the relative a* index difference (Deltaa*) image showed less erythema in PWS skin after laser treatment when compared to pre-treatment values. CONCLUSIONS: Our cross-polarized imaging system and color image analysis method is a simple, noncontact technique that can indirectly provide quantitative measurement of erythema and melanin content in PWS skin.

Algorithms↗

PubMed2001

Identification of cervical intraepithelial neoplasia (CIN) using UV-excited fluorescence and diffuse-reflectance tissue spectroscopy.

BACKGROUND AND OBJECTIVE: The diagnostic potentials of ultraviolet-excitation fluorescence spectroscopy and diffuse-reflectance spectroscopy of tissue are assessed in a study to identify cervical intraepithelial neoplasia (CIN) in vivo. A multivariate algorithm is used to classify tissue into normal tissues, CIN I, and CIN II/III categories, based on spectral characteristics of biopsied tissue sites. STUDY DESIGN/MATERIALS AND METHODS: An optical instrument with the capability of measuring fluorescence and diffuse-reflectance spectra from 120 locations uniformly distributed over the surface of the cervix is described. Using this device, these optical spectra of the cervix were measured on women referred for colposcopy due to an abnormal Pap smear. RESULTS: UV fluorescence differentiates CIN II/III lesions from normal squamous tissue with a sensitivity and specificity of 91 and 93%, respectively. CIN I is distinguished from normal tissue with a sensitivity of 86% and a specificity of 87%. CONCLUSION: Optical spectroscopy shows promise for the detection of pre-cancerous cervical lesions in vivo. The fluorescence and reflectance methods are complementary in their ability to differentiate different tissue types, making the use of the two techniques together more diagnostic than the use of either method separately.

Algorithms↗

PubMed1992

Laser reflections from surgical instruments.

The potential hazards to the eye and skin from accidental exposures caused by reflected laser beams from surgical instruments has long been of concern to operating room staff members. Reflectance values for argon neodymium:YAG and CO2 laser wave-lengths were measured from 29 reference surfaces used on surgical instruments. From these measurements, nominal hazard zones could be determined for typical reflection hazards.

Equipment Design↗

PubMed2006

Assessment of simple movements reflects impairment in Huntington's disease.

Clinical rating, caudate atrophy, disturbed movement performance, neuropsychological testing, and age-related genetic disease load (CAG index) are tools that reflect impairment after onset of Huntington's disease (HD). Objectives were to compare scored HD symptoms, results of neuropsychological testing and of instrumental measurement of simple motion sequences, assess caudate atrophy and CAG index, and investigate their relation to each other in 131 subjects of various HD stages. Caudate atrophy and CAG index significantly increased in advanced HD patients. Motor test results significantly differed between HD patients and 49 controls, but not between HD gene carriers and controls. Instrumental test outcomes, scored HD intensity, caudate atrophy, and CAG index significantly correlated to each other. Neuropsychological testing, which we only performed in the HD gene carriers and the previously untreated HD patients, reflected the early appearance of HD symptoms and correlated with the motor test results. Results of our applied instrumental tool measure impaired movement performance, which is not specific for HD, but reflects the various methods assessed and the slowly evolving symptoms of the degenerative process in HD.

Adult↗

PubMed2005

Choice of dietary protein of vegetarians and omnivores is reflected in their hair protein 13C and 15N abundance.

Stable isotopic (15N, 13C) composition of tissues depends on isotopic pattern of food sources. We investigated whether the isotopic compositions of human hair protein and amino acids reflect the habitual dietary protein intake. Hair samples were analyzed from 100 omnivores (selected randomly out of the 1987-1988 German nutrition survey VERA), and from 15 ovo-lacto-vegetarians (OLV), and from 6 vegans recruited separately. Hair bulk and amino acid specific isotopic compositions were analyzed by isotope-ratio mass spectrometry (EA/IRMS and GC/C/IRMS, respectively) and the results were correlated with data of the 7 day dietary records. Hair bulk 15N and 13C abundances clearly reflect the particular eating habits. Vegans can be distinguished from OLV and both are significantly distinct from omnivores in both 15N and 13C abundances. 15N and 13C abundances rose with a higher proportion of animal to total protein intake (PAPI). Individual proportions of animal protein consumption (IPAP) were calculated using isotopic abundances and a linear regression model using animal protein consumption data of vegans (PAPI = 0) and omnivores (mean PAPI = 0.639). IPAP values positively correlated with the intake of protein, meat, meat products, and animal protein. Distinct patterns for hair amino acid specific 15N and 13C abundances were measured but with lower resolution between food preference groups compared with bulk values. In conclusion, hair 13C and 15N values both reflected the extent of animal protein consumption. Bulk isotopic abundance of hair can be tested for future use in the validation of dietary assessment methods.

Adult↗

PubMedDate not supplied

Reflection confocal imaging of type I and type III isozymes of hexokinase in PC12 cells.

Reflection confocal microscopy was used to determine the intracellular distribution of Type I and III isozymes of hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) in PC12 cells; detection was by staining with diaminobenzidine as a substrate for horseradish peroxidase-conjugated antimouse immunoglobulins bound to isozyme-specific monoclonal antibodies. With both isozymes, detection of the staining pattern was significantly enhanced by reflection confocal imaging compared with viewing with transmitted brightfield optics. For Type I, prominent staining of cytoplasmic organelles having a distribution consistent with that of mitochondria was noted. For Type III, intense staining at the nuclear periphery was observed. A distinct punctate pattern along the nuclear surface implied a nonuniform distribution of the Type III hexokinase and may represent preferential association with nuclear pore structures. A study of technical factors involved in optimizing the reflection image was conducted. We demonstrate that both the choice of objective and the thickness of the mounting medium are critical to successful imaging, and we describe a simple test for assessing the suitability of objectives in any system.

Animals↗

PubMedDate not supplied

High temporal and spatial resolution studies of bone cells using real-time confocal reflection microscopy.

Chick and rat bone-derived cells were mounted in sealed coverslip-covered chambers; individual osteoclasts (but also osteoblasts) were selected and studied at 37 degrees C using three different types of high-speed scanning confocal microscopes: (1) A Noran Tandem Scanning Microscope (TSM) was used with a low light level, cooled CCD camera for image transfer to a Noran TN8502 frame store-based image analysing computer to make time lapse movie sequences using 0.1 s exposure periods, thus losing some of the advantage of the high frame rate of the TSM. Rapid focus adjustment using computer controlled piezo drivers permitted two or more focus planes to be imaged sequentially: thus (with additional light-source shuttering) the reflection confocal image could be alternated with the phase contrast image at a different focus. Individual cells were followed for up to 5 days, suggesting no significant irradiation problem. (2) Exceptional temporal and spatial resolution is available in video rate laser confocal scanning microscopes (VRCSLMs). We used the Noran Odyssey unitary beam VRCSLM with an argon ion laser at 488 nm and acousto-optic deflection (AOD) on the line axis: this instrument is truly and adjustably confocal in the reflection mode. (3) We also used the Lasertec 1LM11 line scan instrument, with an He-Ne laser at 633 nm, and AOD for the frame scan. We discuss the technical problems and merits of the different approaches. The VRCSLMs documented rapid, real-time oscillatory motion: all the methods used show rapid net movement of organelles within bone cells. The interference reflection mode gives particularly strong contrasts in confocal instruments. Phase contrast and other interference methods used in the microscopy of living cells can be used simultaneously in the TSM.

Animals↗