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PubMed1992

Possible cometary origin of heavy noble gases in the atmospheres of Venus, Earth and Mars

Models that trace the origin of noble gases in the atmospheres of the terrestrial planets (Venus, Earth and Mars) to the 'planetary component' in chondritic meteorites confront several problems. The 'missing' xenon in the atmospheres of Mars and Earth is one of the most obvious; this gas is not hidden or trapped in surface materials. On Venus, the absolute abundances of neon and argon per gram of rock are higher even than those in carbonaceous chondrites, whereas the relative abundances of argon and krypton are closer to solar than to chondritic values (there is only an upper limit on xenon). Pepin has developed a model that emphasizes hydrodynamic escape of early, massive hydrogen atmospheres to explain the abundances and isotope ratios of noble gases on all three planets. We have previously suggested that the unusual abundances of heavy noble gases on Venus might be explained by the impact of a low-temperature comet. Further consideration of the probable history of the martian atmosphere, the noble-gas data from the (Mars-derived) SNC meteorites and laboratory experiments on the trapping of noble gases in ice lead us to propose here that the noble gases in the atmospheres of all of the terrestrial planets are dominated by a mixture of an internal component and contribution from impacting icy planetesimals (comets). If true, this hypothesis illustrates the importance of impacts in determining the volatile inventories of these planets.

Argon↗
PubMed1985

Regional ventilation in infancy. Reversal of adult pattern.

There is evidence that in infants with unilateral lung disease, oxygenation improves when the good lung is uppermost--the reverse of the situation in adults. We performed krypton-81m ventilation scanning in 18 infants and very young children (11 days to 27 months old) with and without abnormal chest radiographs. Scanning was performed with the subject supine, in the left decubitus posture (right lung uppermost), and in the right decubitus posture (right lung dependent). Fractional ventilation to the right lung fell when that lung was dependent and rose when it was uppermost (P less than 0.001). This pattern was seen regardless of the appearance of the chest radiograph. The distribution of ventilation away from dependent lung regions represents a reversal of the adult pattern, which may be due to differences between infants and adults in lung mechanics and diaphragmatic function. This study adds further weight to the argument that infants and very young children with unilateral lung disease should be positioned with their normal lung uppermost to optimize gas exchange. It also offers a rational explanation for the observation that infants with unilateral gas trapping can be successfully treated by placing them so that the diseased lung is dependent.

Age Factors↗
PubMed1986

Pulsed excimer laser angioplasty of human cadaveric arteries.

Laser angioplasty has been limited by the lack of precise control of thermal and acoustic vascular injury. Pulsed excimer lasers, by contrast, have a capacity to affect target tissue without heat dispersion or damage to surrounding structures. The ablative properties of three excimer wavelengths, krypton fluoride (249 nm), xenon chloride (308 nm), and xenon fluoride (351 nm), were investigated with the use of fresh human cadaveric normal and atherosclerotic femoral arteries. Light and electron microscopy demonstrated clean cuts with histologically normal edges. There was no evidence of either thermal or acoustic damage with any of the wavelengths studied. The depth of ablation varied directly with the number of pulses and inversely with tissue density while the incision width remained constant. The excimer laser appears to offer significant advantages over its conventional counterparts for the ablation of atherosclerotic plaque.

Arteriosclerosis↗
PubMed1981

An investigation of 11C-methane, 13N-nitrous oxide and 11C-acetylene as regional cerebral blood flow agents.

Radioisotopes of xenon or krypton are generally used as the inert diffusible indicators in regional cerebral blood flow (rCBF) studies. These gases have disadvantages when introduced into the body inhalation because of their low solubility in body tissues. The use of 11C-methane, 13N-nitrous oxide and 11C-acetylene as inhalation rCBF agents has been investigated. These gases span a wide range of solubilities: methane is four times less soluble than xenon in body tissues while nitrous oxide and acetylene are respectively 3 and 6 times more soluble. Cerebral blood flow measurements were performed on normal volunteers using the three labelled gases as well as 133Xe. All tracers were administered by inhalation and the cerebral clearance of the gases was monitored by coincidence detection. Uptake in the body was found to be dependent on solubility. The computed blood flow values found using the various indicators were in excellent agreement and were within the normal cerebral blood flow range. The high solubilities of acetylene and nitrous oxide result in a more efficient transfer of tracer from lung to brain than the conventionally used agents. The positron emission is also advantageous for tomographic rCBF measurements.

Acetylene↗
PubMed2002

Gamma scintigraphic evaluation of a novel budesonide dry powder inhaler using a validated radiolabeling technique.

A scintigraphic study was carried out to compare the lung deposition of budesonide delivered via Clickhaler and Turbuhaler dry powder inhalers in healthy volunteers. Validation of Technetium-99m ((99m)Tc) radiolabeling of the budesonide/lactose blend used in the Clickhaler and excipient-free budesonide used in the Turbuhaler was carried out using a multistage liquid impinger, and compared with reference unlabeled devices. Budesonide was quantified using high-performance liquid chromatography and (99m)Tc by scintillation counting. The percentages (SD) of fine particles (<5.5 microm diameter) from radiolabeled and unlabeled devices were not significantly different (p > 0.05). Mean values for drug and radiolabel, respectively, were 34.6% (2.5) and 31.6% (3.8) for the Clickhaler, and 29.8% (5.5) and 31.4% (5 6) for the Turbuhaler. Fifteen healthy male volunteers received a single dose (2 x 200 microg actuations) from both devices in a double-blinded, double dummy, crossover study. During dosing, each inhalation maneuver was recorded using a computer-linked pressure transducer. To permit accurate determination of radiolabeled drug deposition, the lung margins of each volunteer were determined by Krypton-81m ((81m)Kr) gas imaging. Mean [SD] lung deposition for the Clickhaler (26.8% [6.8], RSD 25.2) was significantly greater (p < 0.001) than for the Turbuhaler (15.8% [6.6], RSD 42.2). Inspiratory flow rate parameters were similar for both devices with peak and mean values of 73 and 51 L/min for the Clickhaler, and 73 and 47 L/min for the Turbuhaler, respectively. These results indicate that, in healthy volunteers, budesonide lung deposition was higher and more consistent with the Clickhaler than with the Turbuhaler.

Adult↗
PubMed1996

Scanning electron microscopic analysis of acute photodynamic therapy for atherosclerotic plaques of rabbit aorta by using a pheophorbide derivative.

The aim of this study was to demonstrate acute efficacy of photodynamic therapy on atheromas by using a pheophorbide derivative, PH-1126. Cholesterol-fed atherosclerotic rabbits were injected intravenously with 1 mg/kg of PH-1126. Twenty-four hours later, PH-1126 selectively accumulated in atherosclerotic plaques. Then, atherosclerotic lesions in the upper thoracic aorta were treated by irradiation with a krypton ion laser at a wave-length of 647 nm. At 6 h after photodynamic therapy, the treated aorta was examined by scanning electron microscopy. Numerous teardrop-shaped cells were observed on the endothelial surface of the plaque irradiated at a total energy of 100 J/cm2. These cells were larger than monocytes and macrophages, and resembled foam cells in size and shape. The body of the teardrop-shaped cell resembled pumice stone, mainly because of the presence of globular elements in the cytoplasm. A part of the cell appeared to remain in the subendothelial space. These findings suggest that the cells may be foam cells from the intimal layer of atherosclerotic plaque that were expelled into the aortic lumen. It may become possible to flatten atheroma in a long-term period after photodynamic therapy using PH-1126 as a potent photosensitizer.

Animals↗
PubMed2006

Comparative analysis of different scintigraphic approaches to assess pulmonary ventilation.

A study was carried out to investigate the predictive value of 81-metastable-krypton (81mKr) distribution, high-size 99-metastable-technetium (99mTc) aerosol deposition and low-size 99mTc aerosol (Technegas) deposition on the pulmonary ventilation evaluated by 133-xenon (133Xe) lung scintigraphy, and to assess the correlation between the 81mKr distribution, the 99mTc aerosols deposition, and the respiratory parameters of patients with chronic obstructive pulmonary disease (COPD). Twenty COPD patients were included. The 81mKr, 133Xe, and 99mTc aerosol lung scintigraphies were successively carried out. The 81mKr distribution and 99mTc deposition were compared to the 133Xe distribution at equilibrium and to the 133Xe clearance. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 81mKr and Technegas lung scintigraphies to detect alterations in ventilation revealed by 133Xe were defined. The 81mKr distribution and 99mTc deposition according to respiratory parameters were described using a principal component analysis. Compared to 133Xe distribution, a significantly higher distribution of 81mKr in the upper parts of the lungs in the more severe patients (p = 0.05), a significantly higher deposition of Technegas in the lower parts of the lungs (p = 0.0008), and a significantly higher deposition in the central parts of the high-size 99mTc aerosol were observed (p = 0.0001). The PPV and the NPV were, respectively, 0.54 and 0.58 for 81mKr and 0.54 and 0.55 for Technegas. There was a significant negative correlation between 81mKr distribution and 133Xe clearance (p = 0.0001) between Technegas deposition and 133Xe clearance (p = 0.0007), and between 99mTc diethylene-triamino-penta-acetate (DTPA) deposition and 133Xe clearance (p = 0.001). Both the 81mKr peripheral distribution and Technegas peripheral deposition correlated negatively with increased obstruction, as measured by forced expiratory volume in 1 sec (FEV1). Peripheral deposition of the high-size 99mTc aerosol deposition correlated with the inspiration/expiration time ratio. In conclusion, 81mKr and 99mTc aerosols' lung scintigraphies do not reflect exactly the pulmonary ventilation as measured by 133Xe scintigraphy.

Aged↗
PubMed1998

Minimum alveolar concentrations of noble gases, nitrogen, and sulfur hexafluoride in rats: helium and neon as nonimmobilizers (nonanesthetics)

UNLABELLED: We assessed the anesthetic properties of helium and neon at hyperbaric pressures by testing their capacity to decrease anesthetic requirement for desflurane using electrical stimulation of the tail as the anesthetic endpoint (i.e., the minimum alveolar anesthetic concentration [MAC]) in rats. Partial pressures of helium or neon near those predicted to produce anesthesia by the Meyer-Overton hypothesis (approximately 80-90 atm), tended to increase desflurane MAC, and these partial pressures of helium and neon produced convulsions when administered alone. In contrast, the noble gases argon, krypton, and xenon were anesthetic with mean MAC values of (+/- SD) of 27.0 +/- 2.6, 7.31 +/- 0.54, and 1.61 +/- 0.17 atm, respectively. Because the lethal partial pressures of nitrogen and sulfur hexafluoride overlapped their anesthetic partial pressures, MAC values were determined for these gases by additivity studies with desflurane. Nitrogen and sulfur hexafluoride MAC values were estimated to be 110 and 14.6 atm, respectively. Of the gases with anesthetic properties, nitrogen deviated the most from the Meyer-Overton hypothesis. IMPLICATIONS: It has been thought that the high pressures of helium and neon that might be needed to produce anesthesia antagonize their anesthetic properties (pressure reversal of anesthesia). We propose an alternative explanation: like other compounds with a low affinity to water, helium and neon are intrinsically without anesthetic effect.

Anesthetics↗
PubMed1982

Evaluation of radiation monitor effectiveness for the detection of 85Kr.

As part of the preparations for the purging of TMI Unit-2, the 85Kr sensitivity of 12 radiation detector systems or system combinations was determined. Eleven of these were evaluated using a cube-shaped polyethylene-walled room containing a volume of 5.6 m3 (200 ft3). Krypton-85 gas was added to produce a concentration of 6.7 x 10(-6) muCi/ml in the test room. It was found that none of the ion chambers and scintillation detector systems were able to detect this concentration of 85Kr. Detectors employing thin window GM pancake probes were found to be sensitive enough to monitor this gas down to the unrestrictive area maximum permissible concentration level (MPC) of 3 x 10(-5) muCi/ml, while a large window gas flow proportional counter was found to be sensitive enough to monitor down to about 09.1 MPC. At the end of this experiment, 2.3 m3 (80 ft3) of the gas in the test room was pumped into a compressed air cylinder (scuba bottle) and was used to calibrate The Pennsylvania State University (PSU) Noble Gas Monitor. The sensitivity of this system, which employs gas compression and Ge(Li) spectroscopy, was demonstrated to be between 0.1 and 0.03 times MPC, depending on the counting time employed.

Air Pollutants, Radioactive↗
PubMed1990

Caustic ingestion and esophageal function.

The aim of the present study was to investigate esophageal motor function by means of krypton-81m esophageal transit scintigraphy and to compare the results with the functional and morphological data obtained by means of triple lumen manometry and endoscopy. In acute and subacute stages of the disease, all clinical, anatomical, and functional parameters were in good agreement, revealing significant impairment. In chronic stages, the severity of the dysphagia was not correlated to the importance of the residual stenosis. Conversely, 81mKr esophageal transit and manometric's findings were in good agreement with the clinical symptoms, during the entire follow-up period ranging between 3 months to 7 years. The 81mKr test is undoubtedly the easiest and probably the most physiological technique currently available for long-term functional evaluation of caustic esophagitis.

Accidents, Home↗
PubMed1986

Pulmonary ventilation and perfusion studies in infants and children.

Ventilation and perfusion imaging techniques may be applied successfully to the diagnosis of many pulmonary disorders in children. These studies may be performed with relative ease and safety in all patients, even if they are unable to cooperate. The choice of radiopharmaceuticals applicable to children includes inert gases such as xenon 133 and krypton 81m as well as technetium 99m particles for perfusion and aerosol ventilation imaging. Quantitation of regional lung function is readily performed with available techniques. The indications for ventilation and perfusion lung imaging in children differ significantly from those in the adult.

Child↗
PubMed1988

Abnormalities of pulmonary blood flow during cold exposure in systemic lupus erythematosus.

The aim is to determine whether pulmonary blood flow is altered during cold exposure of the hands in individuals with systemic lupus erythematosus (SLE). Cold exposure was induced by immersion of the hands, one at a time, in 10 degrees C water in nine SLE patients in whom pulmonary fibrosis had been ruled out by a routine examination. Lung perfusion was measured by continuous venous infusion of krypton 81 m. Cold exposure to at least one of the hands caused an 8 to 22% decrease of pulmonary blood flow in five of the nine patients. A 10 to 33% increase in flow developed in three of the nine patients during cold exposure of the hands. We conclude that these abnormalities in pulmonary blood flow during cold exposure were revealed in SLE patients with scarcely any clinical symptoms.

Adult↗
PubMed1995

The effect on diagnostic quality of using dual isotope imaging for 81Krm ventilation and 99Tcm-MAA perfusion lung scanning.

It is the practice in some centres to use dual isotope imaging to reduce imaging times in lung ventilation and perfusion studies with 81Krm gas and 99Tcm-macroaggregated albumin (99Tcm-MAA) by simultaneous acquisition of the two images. The resulting loss of image caused by cross-talk between the two energy windows was investigated using two phantoms, one with cold 99Tcm lesions of varying size and contrast, and the other a uniform field of 81Krm. It was found that, under scatter conditions typical of a patient study, the use of dual isotope acquisition and a krypton generator of 470 MBq or greater resulted in a perceptible loss of image quality with lesions up to 4 cm in diameter being missed. On an older camera system, without modern energy and linearity correction facilities, a lower generator activity of only 120 MBq was sufficient to cause image degradation even under very low scatter conditions. Seventy-five patient studies were performed using both single and dual isotope imaging with generator activities ranging from 80 to 282 MBq. At these low generator activities, the studies did not demonstrate any differences between the images that would result in a different diagnosis. We conclude that the use of dual isotope V/Q scanning reduces the diagnostic value of the perfusion image if the activity of the 81Krm generator is too high, although at generator activities of 300 MBq or less no loss of image quality will occur on modern camera systems.

Humans↗
PubMedDate not supplied

Treatment of combined traction-rhegmatogenous retinal detachment in the morning glory syndrome.

A 14-year-old boy had a near total retinal detachment associated with the morning glory optic disc anomaly. A tiny slit-like retinal break with adjacent vitreous traction was found within the coloboma, providing communication between the vitreous cavity and the subretinal space. Vitrectomy, fluid-gas exchange, and postoperative confluent Krypton laser photocoagulation around the optic disc resulted in a successful reattachment of the retina. The retina has remained attached for 14 months.

Adolescent↗
PubMed2001

Generation of noble-gas binding sites for crystallographic phasing using site-directed mutagenesis.

In recent years, the use of noble-gas complexes for the de novo phasing of protein structures has proven to be a useful alternative to selenomethionine and more traditional derivatives, largely owing to improvements in methods for incorporating noble gases within protein crystals. Advantages of noble-gas derivatives include a high degree of isomorphism when using xenon for multiple isomorphous replacement (MIR) and an easily accessible absorption edge when using krypton for multiwavelength anomalous dispersion (MAD) phasing. One problem with this approach is that not all proteins contain cavities which bind noble gases. Even in proteins which do bind noble gases, the resulting derivative may not be sufficient for phasing. Using T4 lysozyme as an example, it is illustrated how this limitation might be overcome by using 'large-to-small' mutations to introduce potential noble-gas binding sites. Wild-type T4 lysozyme contains a single xenon-binding site. By truncating leucine and phenylalanine residues to alanine, it is possible to generate additional noble-gas binding sites within the core of the protein. Combining rotating-anode data from xenon complexes of wild-type and mutant lysozymes yields MIR phases which compare favorably with those determined from a selenomethionine MAD experiment conducted at a synchrotron. Experience with T4 lysozyme suggests that a leucine-to-alanine substitution made at random in a protein of unknown structure has about a 30% chance of providing a useful derivative. This procedure holds promise for the determination of unknown protein structures, especially when selenomethionine-containing protein is not available or when access to a synchrotron is limited.

Bacteriophage T4↗
PubMedDate not supplied

Intensifying screen for xeroradiography.

A high-atomic-number rare gas has been incorporated into xeroradiographic cassettes in order to increase the sensitivity of the process to x radiation. Preliminary results indicate that krypton gas at 1-atm pressure increases the sensitivity by approximately a factor of 2 in the mammography energy region.

Krypton↗
PubMedDate not supplied

Amplification and entailed resolution degradation in high-pressure gas ionography.

This work deals with the introduction of a gas electronic gain factor in high-pressure ionography (or "electron radiography"). The purpose is to check the possibility of a further reduction of radiation dose per radiograph. It is shown tha xenon or krypton can be mixed with special molecular gases in order to achieve charge-carrier multiplication at comparatively weak electrostatic fields and in an easily controllable manner. Some radiographs are reproduced which have been obtained in the amplifying working modes of the system. Relevant image characteristics and their limits are discussed. The obtainable resolution is limited by electron diffusion and by quantum noise (lowering of the effective quantum-detection efficiency).

Electrodiagnosis↗
PubMedDate not supplied

Laser fluorescence bronchoscope for localization of occult lung tumors.

A system for imaging occult bronchogenic carcinoma by the fluorescence of previously-injected, tumor-specific compound hematoporphyrin-derivative has been assembled and successfully used to locate a tumor 1 mm thick. The violet excitation source is a krypton ion laser coupled to fused quartz fiber light conductor. An electrostatic image intensifier attached to a standard flexible fiberoptic bronchoscope provides a bright image even at relatively low irradiance. A red secondary filter rejects most reflected background and autofluorescence. Sensitivity and contrast capability of the system should permit detection of a tumor less than 0.1 mm thick.

Bronchoscopes↗