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PubMed2004

Phytochrome A: functional diversity and polymorphism.

Phytochrome (phy), a 124 kDa biliprotein, mediates plants' perception of environmental light conditions including quantity, quality and duration of light. The complex phenomenology of phy function is connected with its polymorphism, the major phys being phyA and phyB. PhyA mediates irreversible photoresponses in the very low and high fluence ranges (VLFR and HIR) primarily in the far-red (FR) spectral region, whereas phyB mediates the 'classical' R/FR reversible responses in the low fluence range (LFR). This phyA specificity is determined at the level of (i) intramolecular events, (ii) turnover, phyA being light-labile, and (iii) nuclear-cytoplasmic partitioning and interaction with partner proteins. A unique feature of phyA is that two native isoforms, phyA' and phyA'', comprise it, distinguished by spectroscopic and photochemical properties, localization and abundance in plant tissues, light stability, and other properties. They differ by the post-translational modification at the 6 kDa N-terminus, possibly phosphorylation, phyA' being phosphorylated and phyA'' dephosphorylated. Both species participate in the light-induced nuclear-cytoplasmic partitioning. The light-labile phyA' is responsible for de-etiolation (VLFR and HIR modes), whereas the relatively more light-stable phyA'' could be active throughout the whole life cycle. PhyA'' interferes with the action of phyA' and this interaction may be part of the fine tuning mechanism of the phyA function. Finally, within the phyA' pool there are different conformers in thermal equilibrium, that differ by the activation and kinetic parameters of the Pr-->lumi-R photoreaction. This heterogeneity of phyA may account, at least partially, for the complex dynamics of its photoprocesses and the phenomenology of photoresponses.

Genetic Variation↗
PubMed1998

Visual dysfunction in HIV-positive patients without infectious retinopathy.

Persons with HIV disease are susceptible to various manifestations of retinal damage, such as infectious retinopathies (e.g., cytomegalovirus [CMV] retinitis and toxoplasmosis) and noninfectious complications (microangiopathic infarctions or cotton-wool spots [CWS]); CWS being quite common in AIDS patients. Until recently, little research focused on noninfectious ocular pathology in HIV disease. These disorders may all affect normal functioning of the visual system while funduscopic examination results appear normal. A review of the psychophysical changes, color and contrast sensitivity, peripheral visual function, electrophysiologic and morphologic changes, the relationship of vision loss and neuropsychological changes, postretinal damage, and imaging capabilities cast important new light on quality of life issues and vision function for all HIV/AIDS patients regardless of CD4 count, other measures of wellness, or treatment protocols. Entopic perimetry, a low-cost psychophysical technique screening test, allows sensitive and specific identification of very peripheral areas of visual field loss. The authors recommend its implementation and use by primary care providers, particularly for early detection of retinal damage when funduscopic examination results may appear normal.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Noninvasive laser-based blood pressure measurement in rabbits.

To obtain serial blood pressure measurements without trauma in rabbits, we developed a laser-based method which permits noninvasive determination of systolic and diastolic arterial blood pressure. The ease and accuracy of this method were evaluated over a range of blood pressures in five New Zealand White rabbits. Laser-based pressures from the central ear artery were compared with cannula-based pressures from the contralateral central ear artery. Pressures were measured before and during infusions of saline (control), nitroprusside, or epinephrine, and following induction of anesthesia. Noninvasive measurements correlated highly with direct measurements (systole: r = 0.89; diastole: r = 0.93). The difference between the non-invasive and direct pressure measurements during saline, nitroprusside, and epinephrine infusions, and following anesthesia, respectively, were (mean +/- SD, systole/diastole): 4.2 +/- 2.4 (P = NS)/9.3 +/- 1.4 (P less than .001), 4.1 +/- 1.6 (P less than .02)/3.2 +/- 1.1 (P less than .01), 0.6 +/- 2.4 (P = NS)/-3.0 +/- 2.7 (P = NS), and -5.1 +/- 2.9 (P = NS)/0.3 +/- 1.3 (P = NS). The noninvasive method did not result in observable agitation of the animals. To optimize results, visual inspection was required to assure that the instrument's diaphragm was not deformed or dried from previous use, and that the diaphragm was placed over the center of the arterial lumen. It was also necessary to dim room lights and to direct heating lights away from the ears to avoid degrading light signal quality. These results, albeit involving a small number of animals, indicate the potential utility of this method in the study of chronic pathophysiological processes requiring long-term repeated determination of systolic and diastolic blood pressure.

Animals↗
PubMed2004

On the 710 nm fluorescence emitted by the diatom Phaeodactylum tricornutum at room temperature.

The fluorescence emitted at 710 nm by Phaeodactylum tricornutum (F(710)) was characterized. Development of F(710) was found to be regulated by the quality of light needed for algal growth: weak red light absorbed mainly by Chl a induced its development, and weak blue-green light absorbed mainly by fucoxanthin and Chl c suppressed it. The difference spectra between cells grown under the two light conditions revealed two Chl a forms, absorption peaks of which were located at 692 nm (Chl a(692)) and at 703 nm (Chl a(703)), respectively, in red-light-grown cells. During cell growth under red light, the appearance and intensification of the emission correlated well with development of Chl a(692) and Chl a(703) suggesting that the two forms of Chl a are involved in the energy flow to F(710). A clear induction phenomenon characteristic of the PSII fluorescence was observed not only with the emission at 680 nm but also with F(710), indicating that F(710) is emitted by PSII Chl a. Development of F(710) under red light was sensitive to cycloheximide, indicating that the development of the energy flow to F(710) requires protein synthesis and that the emitter is installed in a protein encoded in the nuclear genome like the light-harvesting complex (LHC). Centrifugal fractionation of pigment-protein complexes revealed F(710) to be located at fractions slightly heavier than the major LHC. Development of F(710) was also found in red-light-grown cells of the diatom Nitzschia closterium.

Cells, Cultured↗
PubMed2002

Midday stomatal closure in Norway spruce--reactions in the upper and lower crown.

We used local microclimatic conditions and twig sap flow rates to interpret midday stomatal closure in the canopies of two 250-year-old Norway spruce (Picea abies (L.) Karst.) trees at a subalpine site in the Swiss Alps (1,650 m a.s.l.). Both trees showed midday stomatal closure on most clear summer days, despite the permanently wet soil. We used a modified Penman-Monteith formula to simulate potential transpiration of single twigs (ET(T)) based on high-resolution temporal and spatial microclimate data obtained both inside and outside the crowns. Comparison of calculated ET(T) values and measured twig sap flow rates enabled us to pinpoint the occurrence of midday stomatal closure and the microclimatic conditions present at that time. We found that vapor pressure deficit (and for upper-crown twigs, ET(T)) largely explained the timing of initial midday stomatal closure but gave no explanation for the different patterns of stomatal behavior after initial closure in upper- and lower-crown twigs. After the initial stomatal closure, upper-crown twigs maintained high transpiration rates by continuously regulating stomatal aperture, whereas stomatal aperture decreased rapidly in lower-crown twigs and did not increase later in the day. Midday stomatal closure in lower-crown twigs occurred on average 1 h later than in upper-crown twigs. However, the microclimate at the time of initial stomatal closure was similar at both crown locations except that lower-crown twigs received significantly less solar radiation than upper-crown twigs both at the time of initial stomatal closure and afterwards. High rates of sap flow in twigs did not always lead to stomatal closure and therefore could not explain the phenomenon. We conclude that stomatal conductance can be modeled accurately only when both local microclimatic conditions and tree water status are known. Further, we hypothesize that both the quantity and quality of light play an important role in the reopening of closed stomata during the day.

Biomass↗
PubMed1998

Accuracy of continuous jugular bulb oximetry in the intensive care unit.

OBJECTIVE: To address the accuracy of a bedside jugular bulb oxygen saturation (SjO2) catheter monitor (Baxter-Edwards, Santa Ana, CA) versus in vitro co-oximetry measurements in the intensive care unit (ICU). METHODS: By prospective protocol, we compared blood gas measurements with simultaneously recorded continuous bedside oximetric monitor values for 31 ICU patients with traumatic brain injury undergoing jugular bulb catheter monitoring. For suboptimal fiberoptic light signal quality indices, the catheter was repositioned, flushed, or both before drawing the sample for in vitro measurement. Laboratory and bedside monitor data were examined for association using the chi2 and paired t tests and a linear regression model. RESULTS: We assessed 195 samples (median, 5 per patient; range, 1-14) who were monitored an average of 3.4 (range, 1-6) days. The in vivo monitor (range, 32-94%) and in vitro co-oximetry (range, 38-93%) values had acceptable correlation (y = 0.94x + 4.4, r2 = 0.80). For bedside monitor detection of jugular bulb desaturation (SjO2 < 50% for 10 min), the kappa statistic was 0.35, the sensitivity was 45 to 50%, and the specificity was 98 to 100%. CONCLUSION: Continuous ICU SjO2 monitoring correlates significantly with in vitro values, but less so than previously described during intracranial surgery. Although sensitivity of the bedside monitor to detect confirmed desaturations remains an issue, the high specificity indicates that it is less of a concern that patients may be misdiagnosed as having desaturations resulting in unnecessary interventions. Nonetheless, suspected jugular bulb desaturation should be verified before taking therapeutic actions.

Adolescent↗
PubMed1977

Effects of Quality, Intensity, and Duration of Light Breaks during a Long Night on Dormancy in Blue Spruce (Picea pungens Engelm.) Seedlings.

Blue spruce (Picea pungens Engelm.) seedlings grow continuously when exposed to photoperiods exceeding 16 hours and enter dormancy within 4 weeks under photoperiods of 12 hours or less. Dormancy was prevented under 12-hour photoperiods by 2-hour light breaks of red light (1.70 muw/cm(2) at 650 nm) or high intensity white light (2,164.29 muw/cm(2) at 400 to 800 nm) given in the middle of the 12-hour night, and by continuous low intensity white light (204.76 muw/cm(2) at 400 to 800 nm). Two-hour light breaks of far red light (1.80 muw/cm(2) at 730 nm), red light followed by far red light, or low intensity white light were not effective in delaying dormancy. The results imply that the phytochrome system mediates the photoperiodic control of dormancy in blue spruce seedlings. The similarity of results obtained using the low intensity, long duration as against the high intensity, short duration light treatments suggests that the law of reciprocity applies in this response.

Journal Article↗
PubMed1986

Controls for flow cytometers in hematology and cellular immunology.

The necessity of using freshly prepared biological samples to control and calibrate flow cytometers has impeded the utilization of flow cytometry in the clinical laboratory where regulations demand careful control calibration and yet workload and technician training militate against the preparation of specialized control samples. For a number of years, cell preparations with stabilized properties have been used routinely in hematology laboratories to evaluate the daily performance of automated blood cell counters including optical flow cytometers. Unfortunately, the stabilized preparations do not necessarily duplicate many important aspects of whole blood, resulting in variable performance of a given control preparation on different types of instrumentation. The new generation of hematology analyzers measures a host of new parameters and will require more sophisticated controls for these enhanced parameters. Some practical aspects of present and future hematology controls will be discussed. Immunology, a new area for automated cell analysis, can benefit greatly from controls both for instrument performance and for cell staining. Up to this time there has been little availability of control materials suitable for clinical immunology. We have been evaluating fluorochrome-stained cell nuclei for use as an instrument control and for calibration of immunofluorescence analyses. Our development and use of this type of control will be described. We will also discuss approaches and experiments aimed at producing cells with stabilized antigenic properties which can be stained with monoclonal antibodies and can thus act as actual reagent controls.

Antibodies, Monoclonal↗
PubMed2004

Dose response characteristics of new models of GAFCHROMIC films: dependence on densitometer light source and radiation energy.

This paper presents a systematic study of the dose response characteristics of two new models and one commonly used model of GAFCHROMIC film: HS, XR-T, and MD55-2, respectively. We irradiated these film models with three different radiation sources: I-125, Ir-192, and 6 MV photon beam (6 MVX). We scanned the films with three different densitometers: a He-Ne laser with a wavelength of 633 nm, a spot densitometer with a wavelength of 671 nm, and a CCD camera densitometer with interchangeable LED boxes with wavelengths of 665 nm (red), 520 nm (green), and 465 nm (blue). We compared the film sensitivities in terms of net optical density (NOD) per unit dose in Gy. The sensitivity of each film model depends on radiation energy and the densitometer light source. Using He-Ne laser based densitometer as a reference standard, we found the sensitivities (NOD/Gy) for the red lights of wavelengths, 671 nm and 665 nm, are higher by factors of about 2.5 and 2, respectively. The sensitivities for green (520 nm) and blue (465 nm) lights are lower than that for He-Ne laser (633 nm) by factors of about 2 and 4, respectively. The energy dependence of the sensitivity varies with the film model, but is similar for all densitometer light sources. Comparing I-125 to Ir-192 and 6MVX, we note that (a) model XR-T is about eight times more sensitive, and (b) models HS and MD55-2 are about 40% less sensitive. Relative to MD55-2, XR-T is 12 times more sensitive for I-125 but comparable for Ir-192 and 6MVX, whereas HS is 2 to 3 times more sensitive in all cases. This set of results can serve as useful information for making decisions in selecting the film model and compatible densitometer to achieve the best accuracy of dosimetry in the appropriate dose range.

Densitometry↗
PubMed2003

Utilizing an electronic portal imaging device to monitor light and radiation field congruence.

A method to investigate light and radiation field congruence utilizing a commercially available amorphous silicon electronic portal imaging device (EPID) was developed. This method employed an EPID, the associated EPI software, and a diamond-shaped template. The template was constructed from a block tray in which Sn/Pb wires, 1 mm in diameter, were embedded into a diamond shaped groove milled into the tray. The collimator jaws of the linac were aligned such that the light field fell directly on the corners of the diamond. A radiation detection algorithm within the EPI software determined the extent of the radiation field. The light and radiation field congruence was evaluated by comparing the vertexes of the diamond reference structure to the detected radiation field. In addition, the digital jaw settings were recorded and later compared to the light field detected on the films and EPIs. Three linear accelerators were tracked for a period ranging from 2-8 months. Light radiation field congruence tests with films and EPIs were comparable, yielding a difference of less than 0.6 mm, well within the allowed 2-mm tolerance. A disparity was observed in the magnitude of the detected light field. The X and Y dimensions of the light field measured with film differed by less than or equal to 1.4 mm from the digital collimator settings, whereas the values extracted from the EPIs differed by up to 2.5 mm. Based on these findings, EPIs were found to be a quick and reliable alternative to film for qualitative and relative analyses.

Image Processing, Computer-Assisted↗
PubMed1978

Bioaccumulation and detection of trace levels of cadmium in aquatic systems by Eichhornia crassipes.

The water hyacinth (Eichhornia crassipes) may be used as a sensitive biological indicator for continuously monitoring trace quantities of toxic heavy metals in aquatic systems. A river water system polluted with cadmium was simulated while other factors of temperature, day-night cycle, water quality, and light intensity remained constant. When the water hyacinth is maintained in river water containing 0.001 mg/l. of cadmium chloride, the plant's root system will concentrate this element at an average rate of 0.9, 1.4, and 3.0 mug Cd/g root dry weight after 24, 48, and 72 hr exposure periods, respectively. At a higher cadmium concentration of 0.01 mg/l., cadmium was concentrated in the roots much faster to levels of 6.8, 13.6, and 39.1 mug/g root after 4, 8, and 24 hr exposure periods, respectively. At initial concentrations of 0.05 mg/l. cadmium, the roots contained 29.5, 48.8, and 156 mug/g root following 4, 8, and 24 hr exposure periods, respectively. During these same time intervals, the water hyacinth sorbed 56.7, 153, and 281 mug/g root when the initial cadmium concentration was increased to 0.10 mg/l. The water hyacinth tops can also assist in the monitoring process when cadmium contamination levels are 0.10 mg/l. and greater. At this initial cadmium concentration, cadmium is translocated into the tops. After 8 hr, the tops averaged 1.1 mug/g top. After 24 hr, this concentration was increased to 6.1 mug/g top.

Cadmium↗
PubMed2003

Strong Bragg gratings photoinduced by 633-nm illumination in evaporated As2Se3 thin films.

Bragg gratings are used in several photonic devices to reflect, and thus to isolate, specific wavelengths of light. Gratings can be photoinduced in chalcogenide glasses by illumination of bandgap light in an interference pattern. We used holographic interferometry to create Bragg gratings in amorphous As2Se3 thin films with a period of 0.56 microm by illumination with 633-nm light. The quality of the gratings was tested in real time, and refractive-index modulations as high as 0.037 were measured. These gratings were found to be stable over a period of several months if they were kept in the dark.

Journal Article↗
PubMed1979

Illumination of the dental operatory.

With the use of the two types of fixtures described in this paper and some precautions taken to reduce glare, the quality of lighting in the dental operatory can be improved.

Dental Offices↗
PubMedDate not supplied

The use of wavelength-selective plastic cladding materials in horticulture: understanding of crop and fungal responses through the assessment of biological spectral weighting functions.

Plant responses to light spectral quality can be exploited to deliver a range of agronomically desirable end points in protected crops. This can be achieved using plastics with specific spectral properties as crop covers. We have studied the responses of a range of crops to plastics that have either (a) increased transmission of UV compared with standard horticultural covers, (b) decreased transmission of UV or (c) increased the ratio of red (R) : far-red (FR) radiation. Both the UV-transparent and R : FR increasing films reduced leaf area and biomass, offering potential alternatives to chemical growth regulators. The UV-opaque film increased growth, but while this may be useful in some crops, there were trade-offs with elements of quality, such as pigmentation and taste. UV manipulation may also influence disease control. Increasing UV inhibited not only the pathogenic fungus Botrytis cinerea but also the disease biocontrol agent Trichoderma harzianum. Unlike B. cinerea, T. harzianum was highly sensitive to UV-A radiation. These fungal responses and those for plant growth in the growth room and the field under different plastics are analyzed in terms of alternative biological spectral weighting functions (BSWF). The role of BSWF in assessing general patterns of response to UV modification in horticulture is also discussed.

Agriculture↗
PubMed1999

Breast-conserving surgery for invasive cancer: a principle based on segmental anatomy.

As the incidence of breast cancer increases in Japan, breast-conserving surgery becomes an important issue in the light of quality of life. We have demonstrated by 3-D reconstruction studies that ductal carcinoma in situ (DCIS) originates from the terminal duct-lobular unit (TDLU). Normal mammary epithelium anatomically located in the TDLU was shown to be biologically associated with cancerous change, particularly in specimens from patients who subsequently developed invasive carcinoma. Atypical ductal hyperplasia as well as DCIS expressed breast cancer associated antigen, providing further biological evidence that the atypical lesion at the TDLU are premalignant. Intraductal spread of carcinoma was defined as "DCIS was present clearly extending beyond the TDLU, or present prominently within the large ducts," and was classified into 3 grades according to the distribution of carcinoma in the duct-lobular system. We have developed a breast-conserving surgery consisting of quadrantectomy and regional lymph node dissection and immediate volume replacement using lateral tissue-flap (LTF). The quadrantectomy was employed on the basis of segmental anatomy of the duct-lobular system in which breast carcinoma originates. Fairly good cosmetic outcome as well as local control were obtained in the patients who underwent the immediate volume replacement using LTF. It must be emphasized that the quadrantectomy is a radical procedure in the sense that it aims at removal of all the carcinoma cells of the primary tumor.

Breast↗
PubMedDate not supplied

Thermoluminescence detection of irradiated fruits and vegetables: international interlaboratory trial.

An international interlaboratory trial was conducted to validate thermoluminescence methods for detecting irradiated fruits and vegetables. Five products were used in this study. This paper presents the results from prestudy material, homogeneity testing, details of sample preparation, and participants' results. Prestudy results provided a basis for cross comparison of instruments in different laboratories. A wide range of sensitivities, reproducibilities, and signal-to-background ratios were observed. Homogeneity testing showed that the method can distinguish between nonirradiated and irradiated products, including those bleached with 100 J/cm2 artificial daylight, provided that sensitivity rejection criteria are rigorously applied. Blind results were returned by 9 participants in the form of first and second glow integrals and glow ratios for all samples and a qualitative classification for each product. Of the 387 results reported, 327 valid results were obtained from participants. Where valid data were obtained, correct qualitative identifications were made by participants in all cases. Participants' results and homogeneity testing both confirm the validity of the thermoluminescence method for detecting irradiated fruits and vegetables.

Food Irradiation↗