Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Krypton”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 703 records · Page 39Linked to original sources
PubMed1985

Regional tidal volume assessed by gated lung imaging.

We have measured regional lung tidal volumes and functional residual capacities by accumulating and framing iso-volumic images while the patient rebreathes 127Xe. As the lung changes shape during ventilation corrections for changes in geometry were obtained by simultaneous collection of 99Tcm counts from the gated perfusion scan. Regions of interest were made to vary throughout the respiratory cycle so that a region had always the same value of 99Tcm counts. From the corrected 127Xe counts regional tidal volumes (TVr) and functional residual capacities (FRCr) were derived. In patients with established chronic bronchitis and emphysema FRCr were greater and the ratio TVr/FRCr decreased compared with patients with relatively normal static and dynamic lung volumes. Preliminary studies suggest that this ratio was a better discriminator between normal and abnormal regional function than estimates of regional xenon washout. Studies with xenon-133 have contributed to our understanding of the physiology of ventilation but have contributed somewhat less to routine clinical practice. This results in part from the unsatisfactory physical properties of xenon-133. Its relatively low gamma ray energy of 80 keV results in significant self-absorption losses and the activity which may be administered is limited by the radiation dose from the associated beta particles so that relatively poor counting statistics are obtained. With inhaled technetium-99m (99Tcm) microspheres imaging conditions are greatly improved but the distribution of these particles may not equate with the distribution of ventilation particularly if wet particles are used. Moreover, simultaneous microsphere perfusion scans with technetium-99m as a label are impossible. Krypton-81m gas has a suitable energy but the short half-life of the rubidium-81m generator (4.7 h) makes supply difficult and the ultrashort half-life of the krypton-81m gas (13 s) leads to problems in calculating the indices of ventilation. Xenon-127 (127Xe) gas has a more favourable dosimetry profile than xenon-133 because it does not have associated beta particles. Further it has an energy (203 keV) suitable for modern gamma cameras and may be used in the presence of injected 99Tcm microspheres to provide simultaneous ventilation/perfusion imaging. Conventional techniques have assumed that a static image of a dynamic process is adequate. As the lungs move during imaging, some account of this respiratory movement should be made.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Can the diode laser (810 nm) effectively produce chorioretinal adhesion?

In this study, argon green (514 nm), krypton red (647 nm), and diode (810 nm) lasers were used to produce transpupillary photocoagulations on rabbit chorioretina to simulate a retinal buckle treatment. To evaluate the efficacy of the diode laser in creating a retinopexy effect, the morphologic aspects of the acute lesions and scar development were compared. The study of the acute lesions revealed that the chorioretinal thermal damage produced by the argon green laser involved all the retinal layers and the retinal pigment epithelium. The use of the krypton red and the diode lasers resulted in deeper chorioretinal thermal damage. Two months after the treatments, all the lesions resulted in adhesive chorioretinal pigmented scars. However, the diode lesions produced a deeper scar, characterized by marked chorioretinal atrophy.

Animals↗
PubMed2003

Experimental and calculated Stark widths within the Kr I spectrum.

On the basis of the precisely recorded 20 neutral krypton (Kr I) line shapes (in the 5s-5p and 5s-6p transitions), we have obtained the basic plasma parameters, i.e., electron temperature (T) and electron density (N) using our line deconvolution procedure in a plasma created in a linear, low-pressure, pulsed arc discharge operated in krypton. The mentioned plasma parameters have also been measured using independent experimental diagnostics techniques. Agreement has been found among the two sets of the obtained parameters. This recommends our deconvolution procedure for plasma diagnostical purposes, especially in astrophysics where direct measurements of the main plasma parameters (T and N) are not possible. On the basis of the observed asymmetry of the Stark broadened line profile, we have obtained not only its ion broadening parameter (A) which is caused by influence of the ion-microfield over the line broadening mechanism but also the influence of the ion-dynamic effect (D) over the line shape. The separate electron (W(e)) and ion (W(i)) contributions to the total Stark width, which have not been measured so far, have also been obtained. Stark widths are calculated using the semiclassical perturbation formalism for electrons, protons, and helium ions as perturbers.

Journal Article↗
PubMed2006

Double-hadron leptoproduction in the nuclear medium.

The first measurements of double-hadron production in deep-inelastic scattering within the nuclear medium were made with the HERMES spectrometer at DESY HERA using a 27.6 GeV positron beam. By comparing data for deuterium, nitrogen, krypton, and xenon nuclei, the influence of the nuclear medium on the ratio of double-hadron to single-hadron yields was investigated. Nuclear effects on the additional hadron are clearly observed, but with little or no difference among nitrogen, krypton, or xenon, and with smaller magnitude than effects seen on previously measured single-hadron multiplicities. The data are compared with models based on partonic energy loss or prehadronic scattering and with a model based on a purely absorptive treatment of the final-state interactions. Thus, the double-hadron ratio provides an additional tool for studying modifications of hadronization in nuclear matter.

Journal Article↗
PubMed1999

Ultrasound biomicroscopic evaluation of ciliochoroidal effusion after laser treatment.

We evaluated ciliochoroidal effusion (CE) by ultrasound biomicroscopy (UBM) following diode endophotocoagulation at the end of the vitreoretinal surgery. The aim of our study was to assess any differences in the CE morphology following diode endophotocoagulation or transpupillary krypton photocoagulation, and to demonstrate the influence of diabetes and intravitreal surgery on CE formation. Sixty-six consecutive patients were divided in to four groups. Twenty-nine patients with proliferative retinopathy underwent transpupillary krypton photocoagulation; 11 diabetic patients underwent vitreoretinal surgery and diode endophotocoagulation; 18 nondiabetics underwent vitreoretinal surgery and diode endophotocoagulation; 8 consecutive nondiabetic patients were the control group and underwent vitreoretinal surgery, without laser treatment. UBM was performed in the four groups before and after laser treatment, if performed. We determined, by UBM, not only the presence, but also the thickness of CE. CE was present in all the patients treated by laser, diabetics and nondiabetics, and its thickness was not correlated with the number of laser spots (p = 0.28). CE was seen ultrasonically in all the patients undergoing transpupillary photocoagulation or endophotocoagulation, regardless of diabetes and surgical trauma.

Aged↗
PubMed1997

Growth factors in age-related macular degeneration: pathogenic and therapeutic implications.

PURPOSE: To investigate the role of growth factors in choroidal neovascularization in humans with age-related macular degeneration (ARMD) and in rats with choroidal neovascularization produced by krypton laser photocoagulation. METHODS: Autoradiography using 3H-thymidine in laser-treated rats. Light- and electron-microscopic immunocytochemistry using antibodies to several different growth factors and to the fibroblast growth factor (FGF) receptor. Tissues studied included the retinas of rats that had received krypton red laser photocoagulation, which induces formation of choroidal neovascularization 6-8 weeks after laser treatment, choroidal neovascular membranes (CNVMs) removed surgically from humans with ARMD and whole human eyes obtained postmortem with macular choroidal neovascular lesions from ARMD. RESULTS: Nuclei of retinal pigment epithelium (RPE) and choriocapillary cells in laser-treated rats were labeled with 3H-thymidine up to 80 days after photocoagulation, maximally at 2-7 days after laser treatment. At all intervals, RPE cells in treated areas immunolabeled for aFGF and bFGF. Labeling was strongest within lysosomes. RPE cells in untreated regions did not immunolabel for growth factors. RPE cells from CNVMs in the maculas of humans with ARMD also immunolabeled for aFGF and bFGF. Some choriocapillary endothelial cells in human CNVMs became labeled in a regular array along their anteluminal and luminal plasma membranes with anti-bFGF antibodies and, in a similar pattern, with antibodies to the FGF receptor. Finally, serial sections from some CNVMs in ARMD patients were immunostained alternately for bFGF and for vascular endothelial growth factor (VEGF). RPE cells and choriocapillary endothelial cells in these membranes immunostained for VEGF. Many immunostained for both bFGF and VEGF. In whole human eyes with macular CNVMs RPE cells in regions of normal retina did not immunostain for these growth factors. CONCLUSIONS: Several growth factors are not expressed at detectable levels by immunocytochemistry in normal RPE cells in rats or humans but do appear following photocoagulation or the development of CNVMs in ARMD. This suggests that these growth factors have a pathogenic role in choroidal neovascularization. Possibly, bFGF and VEGF act synergistically to accelerate neovascularization. The up-regulation of VEGF in CNVMs is of special interest because up-regulation of this growth factor in other systems appears to be stimulated by tissue hypoxia. Till now, hypoxia has not been considered a major pathogenic agent in the development of CNVMs in ARMD or other macular diseases.

Aged↗
PubMed2003

Photothrombotic middle cerebral artery occlusion and reperfusion laser system in spontaneously hypertensive rats.

BACKGROUND AND PURPOSE: To establish a less invasive and reproducible focal ischemia model in the rat, we adopted a 2-laser system (ie, photothrombosis and YAG laser-induced reperfusion). METHODS: The distal middle cerebral artery (MCA) of spontaneously hypertensive rats was occluded by 568-nm krypton laser and intravenous infusion of the photosensitizing dye rose bengal and was recanalized by 355-nm ultraviolet laser irradiation. Cerebral blood flow was determined by laser-Doppler flowmetry at the penumbral cortex. Infarct volume was determined at 3 days after distal MCA occlusion. RESULTS: Brain temperature determined with infrared thermography was maintained within an acceptable range of approximately 1 degrees C upper shift of the center of brain temperature distribution during krypton or YAG laser irradiation. The average of the values (23 experiments; n=163) of coefficient of variation of infarct volume was 21+/-6%, indicating high reproducibility of this model. After distal MCA occlusion, cerebral blood flow was decreased to 32+/-16% of the control values and was increased to 98+/-21% after YAG laser-induced reperfusion. Infarct volume in these rats was 61+/-18 mm3 (coefficient of variation=30%; n=6). CONCLUSIONS: We have characterized a highly reproducible focal ischemia model utilizing a 2-laser system, one to induce thrombotic MCA occlusion and the other to facilitate reperfusion.

Animals↗
PubMed1977

The effect of granulomatous pulmonary disease in dogs on the response of the pulmonary circulation to hypoxia.

We studied the effect of diffuse granulomatous pulmonary disease on the reponse of the pulmonary circulation to hypoxia in two series of experiments in intact dogs. First, in animals with unilateral disease, vasoconstriction in the diseased lung was compared to that in the contralateral control lung. Second, in animals with bilateral disease, the vasoconstriction of pulmonary shunt pathways was compared to that of the rest of the pulmonary vasculature. We assessed vasoconstriction in each study by measuring the distribution of pulmonary blood flow between the test and control set of vessels during 21 and 12% oxygen breathing. In the first set of experiments, we measured apportionment of the blood flow between the two lungs by bronchospirometry and the krypton bolus method. In normal dogs, hypoxia did not shift blood flow systematically from one lung to the other. In 10 dogs with unilateral disease, general hypoxia increased the proportion of blood flow to the diseased lung. The mean percent of blood flow to the left lung in eight dogs with disease in that lung rose from 29% during air breathing to 32% (P < 0.001). In the second set of experiments, we measured apportionment of the blood flow between shunt pathways and gas-exchanging pathways by a constant infusion of radio-active krypton and the standard shunt formula. In eight dogs with bilateral disease, hypoxia consistently increased the flow through shunt pathways, from a mean value of 10% of pulmonary blood flow to 14% (P < 0.005).Thus, diffuse granulomatous disease causes a decreased vasoconstrictive response to hypoxia both in diseased, gas-exchanging regions and in shunt pathways. In proliferative interstitial pulmonary disease, generalized hypoxia causes shifts in pulmonary blood flow which do not ameliorate but rather worsen the hypoxemia of systemic arterial blood.

Animals↗
PubMed2004

Detection and enrichment of hematopoietic stem cells by side population phenotype.

A flow cytometric procedure has recently been described to isolate hematopoietic stem cells from mouse bone marrow based on the efflux properties of the vital dye Hoechst 33342. The assay defines a subset of cells-termed the "side population" (SP)-by simultaneously measuring fluorescence of the dye at two wavelengths (~450 nm and >670 nm). In this chapter, SP protocols are provided to detect candidate hematopoietic stem cells in mouse bone marrow and human cord blood. In the standard method, SP profiles are readily observed on a stream-in-air cell sorter using 30 mW of 351-356 nm ultraviolet excitation from a krypton-ion laser. Alternatively, SP profiles can be resolved on an analytical flow cytometer with cuvette flow cell using 8 mW of 325-nm ultraviolet excitation from a helium-cadmium laser. The ability to perform the SP assay on an analytical instrument facilitates optimization of staining conditions to identify hematopoietic and other stem cells in a variety of tissues. It is also demonstrated that SP profiles of slightly lower resolution can be obtained on a stream-in-air cell sorter using 100 mW of 407-nm violet excitation from a krypton-ion laser, raising the possibility that with appropriate validation the SP assay could be performed on flow cytometers that are not equipped with ultraviolet lasers.

Animals↗
PubMedDate not supplied

Efficacy of various laser wavelengths in the treatment of clinically significant macular edema in diabetics.

BACKGROUND AND OBJECTIVE: To compare various laser wavelengths: argon green (514 nm), vs krypton red (647 nm), vs frequency doubled Nd:YAG (532 nm), and vs diode (810 nm), for laser photocoagulation treatment in clinically significant macular edema (CSME) in diabetics. PATIENTS AND METHODS: Four different wavelengths were used to sequentially treat 271 eyes of 164 diabetic patients with CSME. Follow up was conducted for a minimum of 6 months (9.8 +/- 1.3 months). Retreatment was performed if residual edema involving the foveal avascular zone persisted at 3 months. RESULTS: Reduction/elimination of CSME was observed in 93.3% of argon-treated eyes, 88.5% in krypton red group, 92.9% with frequency doubled Nd:YAG, and 84.8% with diode laser with no statistically significant difference between the groups (P > 0.05 for all groups). The number of eyes requiring retreatment was highest with the diode laser having 44.3% of eyes requiring retreatment and least with frequency doubled Nd:YAG having only 15.5% of eyes requiring retreatment (P = 0.0002). CONCLUSIONS: All lasers are equally effective in reducing/eliminating CSME. However, Nd:YAG may have an advantage because of requiring fewer retreatments.

Adult↗
PubMed1991

[Treatment of choroidal melanoma using photocoagulation].

The author defines the conditions for treatment of chorioid melanomas by photocoagulation which is restricted only to a small number of tumours. The author describes different therapeutic techniques, using photocoagulation. The success rate of treatment of chorioid melanomas by xenon photocoagulation is 50-60%, similar results are obtained with laser coagulation (maily krypton or a combination of argon and krypton). Treatment with an argon laser alone is not suitable as blue light which forms 70% of the light energy does not penetrate into the chorioid. Green light of the argon laser is suited for use in the first stage of treatment, i. e. for obliteration of retinal and chorioid vessels. The authors treated six patients with melanoma of the chorioid using combined xenon-argon therapy. During the average observation period of six years only one patient developed regression of the tumour, in another patient further growth ceased, but regression was not observed. In four patients on account of progression of the tumour the eye had to be enucleated.

Choroid Neoplasms↗
PubMed2004

Selecting an external light source for fetal biophysical testing.

OBJECTIVE: To select the most intense light source that penetrates tissues and is safe for fetal biophysical testing STUDY DESIGN: A 3-step series of experiments was undertaken using a digital light meter (Extech Light Probe Meter, Extech Instruments, Waltham, Massachusetts). First, the density of light through a light filter was compared between the sun and 4 commercially available light sources. Second, penetration of light through the abdominal subcutaneous tissue (3-4 cm thick) of 6 pigs was compared between these light sources. Last, the skin reaction to the preferred light source and the distance in penetrating the uterine cavity were assessed in 50 pregnant women. RESULTS: Light emitted from a halogen bulb was significantly more intense than from a photographic flash, krypton bulb or penlight. Maximal intensity was gained with the light source placed against the skin. The halogen bulb penetrated a pig's abdominal wall more than the photographic flash or krypton bulb. The thickness of a pig's abdominal wall is similar to the distance in pregnant humans near term from the skin to the uterine cavity. No thermal injury or discomfort to the skin was observed for exposures <10 seconds. CONCLUSION: The halogen bulb was safe, penetrated tissues most effectively and was the best light source for fetal biophysical testing.

Abdomen↗
PubMed2004

[Expression and signification of pigment epithelium-derived factor in experimental choroidal neovascularization of rat].

OBJECTIVE: To investigate the expression and signification of pigment epithelium-derived factor in choroidal neovascularization (CNV) induced by krypton laser on Brown Norway rat. METHODS: Five groups of 30 rats were photocoagulated by krypton laser in single eye to induce CNV. 3 days, 1 week, 2 weeks, 3 weeks and 4 weeks after photocoagulation, The retina was processed for histopathology, in situ hybridization of PEDF mRNA, immunohistochemistry of PEDF and FVIIIR:Ag. RESULTS: CNV was formed 1 week after photocoagulation, and reached its peak at 3 weeks. PEDF mRNA, PEDF expressed in the ganglion cells, inner nuclear layer, retinal pigment epithelial cells in normal BN retina. After photocoagulation, the expression of PEDF mRNA and PEDF was observed in the ganglion cells, inner nuclear layer, retinal pigment epithelial cells, and the lesions of outer nuclear layer and choroid; the expression of PEDF in the lesions was weaker than that at the edge of the lesions. From 3 days to 4 weeks, the expression density of FVIIIR:Ag gradually increased, however, the expression density of PEDF mRNA and PEDF in the lesions decreased (P < 0.05). The expression of FVIIIR:Ag was inversely correlated with that of PEDF during the development of CNV (r = -0.84, P < 0.05). CONCLUSIONS: CNV is inversely correlated with PEDF. The down-regulation of PEDF may be one of the main reasons for the formation and development of CNV.

Animals↗
PubMed2004

[Expression of vascular endothelial growth factor and its receptor in experimental choroidal neovascularization in rat].

OBJECTIVE: To study the expressions of vascular endothelial growth factor and its receptor FLK1 in krypton laser-induced choroidal neovascularization (CNV) in Brown Norway rat. METHODS: Thirty anesthetized male Brown Norway rats received krypton laser (647 nm, 360 mW, 50 micro m, 0.05 s) to induce CNV. Fundus fluorescein angiography examinations were performed just before euthanasia on days 3, 7, 14, 21, 28 and 56 after laser photocoagulation. The retina was processed for histopathology analysis. VEGF mRNA, VEGF and FLK1 expressions were demonstrated using in situ hybridization and immunohistochemistry staining respectively. RESULTS: VEGF mRNA expression was mainly observed in the vascular endothelial cells, the ganglion cells, the inner nuclear layers, the retinal pigment epithelial cells in normal retina and the vascular endothelial cells of normal choroid of BN rat. VEGF mRNA expressed in the vascular endothelial cells, the ganglion cells, the inner nuclear layers, lesion of outer nuclear layers in retina on days 3 after photocoagulation, but CNV wasn't detected. The level of VEGF mRNA expression in retina was decreased after 3 days (P < 0.01). CNV was firstly observed on day 7 after photocoagulation by FFA and histopathology. The area and density of positively stained cells for VEGF mRNA in CNV were increased during the development of CNV (P < 0.01) and no significant change after days 21 (P > 0.05). FLK1 was detected in the vascular endothelial cells, the ganglion cells of normal retina and the vascular endothelial cells of choroid. The staining of FLK1 was positive in laser induced CNV after days 7, the level of the receptor expression was increased during the development of CNV (P < 0.01) and was not significantly changed after days 21 (P > 0.05). CONCLUSIONS: VEGF and its receptor FLK1 accumulation and combination in the lesion of retina and choroid are related to choroidal neovascularization induced by laser.

Animals↗
PubMed1988

Retinal pigment epithelial tears. Patterns and prognosis.

Increasing experience with the diagnosis of retinal pigment epithelial (RPE) tears has led to expanded recognition and understanding of this clinical entity. The authors report 18 RPE tears followed for an average of 28 months; 16 were associated with age-related macular degeneration and 2 with presumed ocular histoplasmosis syndrome. Retinal pigment epithelial dehiscences fell into four categories: nine spontaneous tears associated with choroidal neovascularization, one tear associated with an RPE detachment without choroidal neovascularization, four iatrogenic tears occurring at krypton treatment of choroidal neovascularization, and four iatrogenic tears developing weeks to months after laser treatment of choroidal neovascularization. Eight patients had a final visual acuity of 20/100 or better, four were 20/200, and six were 20/400 or worse. Photocoagulation, particularly with the use of krypton red laser, may be modified on the basis of possible RPE tear formation. Heightened awareness of the possibility of inducing pigment epithelial rips should improve diagnosis and management of these cases.

Adult↗
PubMed1988

Current management of choroidal neovascularization.

Age-related macular degeneration is the leading cause of blindness in Americans over age 65. In 1982, the Macular Photocoagulation Study (MPS) established that argon laser photocoagulation reduces the risk of severe visual loss in eyes with extrafoveal choroidal neovascularization (CNV) associated with macular degeneration. Subsequently, similar results were found for histoplasmic and idiopathic choroidal neovascularization. There are also encouraging data on photocoagulation of CNV in other diseases and with different wavelengths. The MPS Group has found the krypton laser to be effective for juxtafoveal CNV secondary to histoplasmosis and is evaluating argon green and krypton red lasers for subfoveal CNV. Other investigators are evaluating laser treatment of CNV associated with myopic degeneration, pigment epithelial detachment, and angioid streaks. The new tunable dye laser may further expand our ability to treat this disorder. Until CNV can be prevented, laser photocoagulation remains the treatment of choice, and clinical trials should identify appropriate cases.

Age Factors↗
PubMedDate not supplied

[Treatment of choroidal neovascularization in degenerative myopia].

Choroidal neovascularization is quite frequent in degenerative myopia. If the neovascularization is near the center, a krypton laser photocoagulation can be effected. If they reach the center, no photocoagulation should be effected. We report here our results in the treatment by krypton laser and describe a simple technic for the determination of the exact position of the foveola, that can be displaced in degenerative myopia.

Adult↗
PubMedDate not supplied

Effects of almitrine on the regional distribution of ventilation and perfusion in chronic bronchitis.

A double-blind, placebo-controlled, crossover study of the effects on regional lung function of oral almitrine bismesylate at a dose of 3 mg X kg-1, was carried out in six patients with severe chronic airflow obstruction. Oxygen saturation (SaO2) was measured by ear-lobe oximetry and ventilation (VE) by inductance plethysmography. Radionuclide ventilation images of the lungs were obtained using krypton-81m by inhalation and perfusion images using both krypton-81m, by i.v. infusion, and technetium-99m human serum albumin macro-aggregates. The images of ventilation, blood flow and VA/Q ratios were analysed in several ways to see if distributional changes explained the improvement in oxygen saturation. SaO2 improved by 6% and VE was 19% greater after almitrine than after placebo. There was no significant change in the distribution of ventilation, perfusion or VA/Q between any of 10 horizontal slices through the left lung. The average position of ventilation distribution was shifted towards the top of the lung compared to placebo (p less than 0.05). No significant changes in distribution of perfusion were observed. We conclude that almitrine is not associated with any change in the inter-regional distribution of perfusion, but may have a slight effect on the distribution of ventilation.

Almitrine↗