Diagnostic Tracer Research Articles

Seasonal changes in the transport of pollutants into the Arctic troposphere‐model study

In association with Tropospheric Ozone Production about the Spring Equinox (TOPSE) measurement campaign a regional episodic chemical transport model is used to study the seasonal mechanisms of transport of pollutants from their Northern Hemisphere emission regions into the remainder of the troposphere. The model simulates the strong seasonal cycle for CO and hydrocarbons that agrees well with TOPSE measurements. In this study we use the isentropic perspective to analyze transport during different seasons and from different emission regions. Simulations with diagnostic tracers are conducted to quantify (1) the contribution of different emission regions to tracer distribution and (2) the importance of cross‐isentropic transport. In the high latitudes during winter, in agreement with previous studies, the European and Siberian emission sources are the largest contributors to the diagnostic tracer distributions in the lower troposphere due to large‐scale circulation patterns, low temperatures at the source and presence of a cold stable boundary layer that facilitates diabatic cooling. North American emissions are located further south, often south of the polar front, and are on average emitted at higher potential temperatures. Owing to their predominant transport over the relatively warm Atlantic, they experience strong diabatic heating due to the general instability in the air column and heavy precipitation in the storm track. During the summer months the pollution from all emission regions is more likely to be diabatically transported to higher potential temperatures and diluted. In addition, direct transport of pollutants into the Arctic is less frequent during summer due to the differences in the large‐scale circulation patterns.

Diagnosing ozone loss in the extratropical lower stratosphere

Chemical ozone loss in the Southern Hemisphere lower stratosphere during winter and spring 1996 is investigated using a three‐dimensional chemical transport model. Model diagnostic quantities are developed to determine the underlying chemical mechanisms controlling the distribution of ozone. These diagnostic tracers quantify the ozone change due to individual catalytic cycles or reaction mechanisms that form or destroy ozone. Results from these tracers confirm the importance of halogens not only in the development of the ozone hole but also in midlatitude ozone depletion of which almost 50% is due to cycles involving halogens. The dominant chemical ozone loss mechanism in the middle latitudes is due to the cycle whose rate determining step involves the bimolecular collision between HO2 and O3. Observational evidence from ozonesonde measurements shows substantial ozone depletion in the polar subvortex region (altitudes below ∼14 km). These measurements also indicate that this ozone depletion must be due, at least in part, to in situ chemical ozone loss. Model results show that over a quarter of the ozone depletion associated with the ozone hole resides at subvortex altitudes. Diagnostic tracers designed to quantify ozone loss occurring above and below the subvortex transition altitude show that the majority of this ozone depletion is in situ ozone loss. Furthermore, at altitudes below the subvortex transition, polar ozone loss is efficiently transported to middle latitudes, where it contributes to midlatitude ozone decline.

The composition and sources of PM 2.5 organic aerosol in two urban areas of Chile

Fine particle (PM 2.5) samples were collected, using a charcoal diffusion denuder, in two urban areas of Chile, Santiago and Temuco, during the winter and spring season of 1998. Molecular markers of the organic aerosol were determined using GC/MS. Diagnostic ratios and molecular tracers were used to investigate the origin of carbonaceous aerosols. As main sources, road and non-road engine emissions in Santiago, and wood burning in Temuco were identified. Cluster analysis was used to compare the chemical characteristics of carbonaceous aerosols between the two urban environments. Distinct differences between Santiago and Temuco samples were observed. High concentrations of isoprenoid (30–69 ng m −3) and unresolved complex mixture (UCM) of hydrocarbons (839–1369 ng m −3) were found in Santiago. High concentrations of polynuclear aromatic hydrocarbons (751±304 ng m −3) and their oxygenated derivatives (4±2 ng m −3), and of n-alk-1-enes (16±13 ng m −3) were observed in Temuco.

Characterization and MRI study of surfactant-coated superparamagnetic nanoparticles administered into the rat brain

A pre-clinical study has been carried out for the utilization of magnetite (Fe 3O 4) nanoparticles as a diagnostic tracer for MRI. Surfactant-coated Fe 3O 4 nanoparticles have been synthesized by a chemical coprecipitation method with a narrow particle size of around 6 nm. Preliminary experiments demonstrated the feasibility of using superparamagnetic Fe 3O 4 nanoparticles as contrast agents in MR imaging.

Radiocarbon as a diagnostic tracer in ocean and carbon cycle modeling

Models which are used to study the evolution of oceanic anthropogenic CO2 uptake in a warmer climate need to be adequately tested before their results are used to influence science and national policy, let alone predict future regional climate. In order to study circulation and the redistribution of carbon in the ocean, we have simulated the uptake and redistribution of bomb radiocarbon in a state of the art ocean general circulation model. The model does reasonably well in simulating the gross surface prebomb distribution of radiocarbon as well as some of the finer details resolved during Geochemical Ocean Section Study and World Ocean Circulation Experiment observations. In areas of downwelling the simulated surface‐ocean bomb 14C maxima occur too early with too much amplitude. This indicates inadequate vertical mixing and coupling between the wind driven and deeper regions of the ocean with a piling up of radiocarbon and CO2 in the upper ocean. This inadequacy will hamper efforts to predict ocean CO2 uptake on decadal to centennial timescales, the equivalent ventilation time of the respective water masses. These results are not specific to our model and indicate a systemic problem in many ocean models.

Re-Os isotope characteristics of postorogenic lavas: Implications for the nature of young lithospheric mantle and its contribution to basaltic magmas

Re-Os isotopes have been measured on postorogenic potassic lavas from the Tibetan Plateau, the Betic domain of southeastern Spain, and the Colorado Plateau of the southwestern United States. Previous work has established that these lavas were all derived from parts of the subcontinental lithospheric mantle that had undergone metasomatic enrichment in incompatible elements, following various degrees of melt depletion. Cratonic depleted subcontinental lithospheric mantle peridotites typically have subchondritic 187 Os/ 188 Os; however, the postorogenic lavas are characterized by radiogenic 187 Os/ 188 Os ratios (0.139‐0.559). Simple modeling shows that only very large degrees of melt depletion (>25%‐30%) can lower source Re/Os ratios sufficiently to permit timeintegrated development of subchondritic 187 Os/ 188 Os ratios. Such processes may have been largely restricted to the older Precambrian, and the peridotite component of the postorogenic lavas source was probably depleted by <25%. The more radiogenic values may reflect increasing contributions from metasomatic components or possibly crustal contamination. Our findings imply the need for caution in the use of Os isotopes as a diagnostic tracer of subcontinental lithospheric mantle contributions to lavas erupted through younger Proterozoic and Phanerozoic lithosphere.

Characterizing the uniformity of polystyrene and TPX z-pinch fusion targets by nuclear microscopy

Fusion research at Sandia’s z-pinch accelerator has produced an X-ray radiation source with a confirmed equivalent black body temperature of 1.8 000 000°C and an output of about 290 terawatts. This radiation source was created by containing the X-rays produced by a z-pinch plasma implosion in a special type of wire array radiation case, about the size of a spool of thread. By placing annular or cylindrical foam targets inside the wire array (a concept called dynamic or internal hohlraum), even higher temperatures can be attained by the rapidly compressing volume. The dynamic hohlraum as an X-ray source places stringent requirements on the quality of foam targets to minimize plasma instabilities during implosion. Nuclear microscopy, which used MeV-energy focused ion beams to characterize materials, provides unique capabilities for quantifying fabrication-induced defects in these targets with fine resolution. For example, the uniformity of representative annular and cylindrical foam targets has been nondestructively characterized in three dimensions by IMT (ion microtomography) with 50–100 μm spatial resolution. The uniformity of very large diameter annular targets (up to 24 mm outer diameter) was measured using STIM (scanning transmission ion microscopy) at several angular orientations. The distribution of diagnostic tracer elements used in some targets to probe the z-pinch plasma was measured by scanned PIXE (particle-induced X-ray emission) and RBS (Rutherford backscattering spectroscopy). The results of these analyses show that high quality foam targets are being delivered for z-pinch experiments, even when target development lead times are as short as 3 weeks.

Scintigraphy with 123I-serum amyloid P component in Alzheimer disease.

The neuropathology of Alzheimer disease (AD) includes cerebral and cerebrovascular amyloid deposits composed of A(beta) protein. Extracerebral deposits of A(beta), identified immunohistochemically, have also been reported but without evidence for the presence of amyloid fibrils. Serum amyloid P component (SAP) is a normal plasma glycoprotein that binds to the fibrils in all types of amyloid deposit, and radiolabeled SAP is a specific, sensitive, quantitative diagnostic tracer for systemic amyloid deposits in vivo. However, we report that in 11 patients with probable or definite AD, conventional whole body planar scintigraphy after injection of 123-SAP revealed no detectable localization of tracer within the brain or elsewhere. Significant amounts of systemic extracerebral A(beta) amyloid are thus probably not a feature of AD. Also, although plasma-derived SAP is always present in the cerebral and cerebrovascular amyloid lesions of AD, there was insufficient accumulation of injected labeled SAP to be detected by the present routine methodology.

Use of Iodine-123 as a Diagnostic Tracer for Neck and Whole-Body Scanning in Patients with Well-Differentiated Thyroid Cancer

To determine whether 123 I can be used as a safe and effective alternative tracer to 131 I for imaging remnant tissue and for searching for metastatic lesions of well-differentiated thyroid cancer. We studied a series of 16 patients (10 women and 6 men; 29 to 73 years of age) who had well-differentiated thyroid cancer and had undergone thyroidectomy and subsequent radioiodine treatment. Diagnostic 10 mCi (either preablation or postablation) were compared with the 5- to 7-day 131 I posttherapy scans (doses, 75 to 200 mCi). Scans were jointly interpreted by nuclear medicine and endocrinology staff members. Of the 16 patients, 15 had concordant findings between the 123 I diagnostic images and the corresponding 131 I posttherapy scans. Only one patient had additional lesions noted on the posttherapy 131 I scan, which was attributed to the higher dose the patient received during radioiodine treatment (a 6% discordance rate). This discordance, however, would not have changed the patient treatment. No advantage was noted for delayed imaging at 48 hours; the 24-hour images were satisfactory. The 123 I scans were of higher resolution than the 131 I scans. Diagnostic 123 I scans are an acceptable alternative to 131 I scanning for whole-body imaging in well-differentiated thyroid cancer and demonstrate adequate imaging of thyroid remnant tissue or metastatic lesions from thyroid carcinoma comparable to the post-therapy scans. 123 I scans also offer greater convenience to patients because they do not have to return for 48- or 72-hour scans. Furthermore, they facilitate earlier institution of therapy by decreasing the interval between diagnostic scanning and radioiodine treatment.

Dynamics of laser-irradiated planar targets measured by x-ray spectroscopy.

The dynamics of planar plastic targets seeded with small amounts of sulfur as a diagnostic tracer is studied spectroscopically. The time-dependent x-ray emission of the hydrogenic and heliumlike sulfur is used to provide a measure of the plasma parameters. The experiment, which is designed to provide optically thin x-ray lines with small transverse gradients, is analyzed by the coupling of a kinetics model to a hydrodynamics simulation. The results of the analysis show that the time histories of the x-ray line intensities can be used as a plasma diagnostic to constrain the modeling. Intensity ratios between ionization stages cannot be accurately modeled even including time-dependent ionization effects. This disagreement appears to be due to detailed assumptions concerning electron distributions and transport.

Radiolabeled L-Fucose for diagnostic oncology: Preliminary studies in mice and rats using l-1- 14C-fucose

Monosaccharides labeled with appropriate gammaemitting radionuclides have a potential for use as diagnostic agents in medicine. Their development has accelerated in recent years because of the successful application of 2-‘8F-fluoro-2-deoxyglucose(‘-5’ in noninvasive, in vivo studies involving humans. To date the use of monosaccharides has been directed primarily towards the elaboration of specific aspects of glucose metabolism, using approaches such as metabolic trapping with 2-‘8F-fluoro-2-deoxyglucose’6’ and “C-deoxyglucose, (‘1 transport with 3-“C-methylD-glucose@ or evaluation of transport sites with 6-radioiodo-D-galactose. (9) In addition, other radiolabeled monosaccharides have been synthesized and tested for their potential as diagnostics in oncology, without a stated specific biochemical objective.“~‘*’ L-Fucose (6-deoxy+galactose) is a monosaccharide which is found throughout the plant and animal kingdoms. In mammalian tissues, it is present primarily in serum and membrane glycoprotein.(‘3.‘4) These fucose-containing glycoproteins are involved in many complex functions, especially as determinants in cellular membranes”” and blood-group substances.“@ Our interest in radiolabeled L-fucose as a diagnostic aid in oncology was based on the conclusion”” that Morris Hepatoma 7777 tumor demonstrated a higher number of free binding sites for fucose and an increased fucose content as compared to host liver tissue. Earlier studies of the suitability of radiolabeled L-fucose as a scintigraphic diagnostic tracer for brain tumors were based on high demand for energy and growth by the tumor.“*) More recently, serum-fucose measurement was proposed as a simple serological test to monitor for recurrent malignancy.“9’

Detection of melanomas. Approach with radiolabeled false precursors of melanin synthesis.

Thiouracil is a thiol-containing pyrimidine that is selectively incorporated into cells that synthesize melanin. In an effort to delineate further the specificity and dynamics of uptake, we injected thiouracil labeled with radioactive carbon into S91 melanoma-bearing mice; biopsy specimens were taken of the tumors and organs at various time intervals thereafter. The data showed a substantial uptake of thiouracil by the melanomas, with peak uptake occurring at 24 hours. All other organs examined showed only minor amounts of radioactivity, which probably reflected the presence of thiouracil in the blood perfusing these tissues. Because of its incorporation into melanomas, the use of radioactive thiouracil has potential as a marker for tumor growth, as a diagnostic tracer compound, and as a carrier for chemotherapeutic agents.

Detection of Melanomas

Thiouracil is a thiol-containing pyrimidine that is selectively incorporated into cells that synthesize melanin. In an effort to delineate further the specificity and dynamics of uptake, we injected thiouracil labeled with radioactive carbon into S91 melanoma-bearing mice; biopsy specimens were taken of the tumors and organs at various time intervals thereafter. The data showed a substantial uptake of thiouracil by the melanomas, with peak uptake occurring at 24 hours. All other organs examined showed only minor amounts of radioactivity, which probably reflected the presence of thiouracil in the blood perfusing these tissues. Because of its incorporation into melanomas, the use of radioactive thiouracil has potential as a marker for tumor growth, as a diagnostic tracer compound, and as a carrier for chemotherapeutic agents.

Dispersal of Mediterranean and Suez Bay sediments in the Suez Canal

This study determines the extent to which sediments of Mediterranean, Suez Bay, and in-situ (authigenic, eroded channel) derivation have been displaced along the Suez Canal. Sediment transport is largely a response to hydrodynamics controlled by markedly different oceanographic conditions at both ends of the channeled byway. Petrology of sand, silt and clay fractions determine distributions of diagnostic tracer minerals. These are used to identify five sediment provinces in the canal which indicate long-term dispersal patterns. Sediments of Mediterranean origin (largely terrigenous from the Nile River) are transported southward to Ballah Bypass, while those of Suez Bay—southern Canal derivation (mixed carbonate and terrigenous) are transported northward to the northern edge of Great Bitter Lake. In-situ derived Bitter Lakes sediments, mostly carbonates, are not transported extensively from the lakes area. Similarly derived Lake Timsah sediment is transported into the short stretches of the canal to the north and south of the lake. The canal south of Little Bitter Lake is a zone of erosion, while the Bitter Lakes are sinks for sediments from several sources.

Investigation of americium-421 metal alloys for target applications

Several 241Am metal alloys have been investigated for possible use in the Lawrence Livermore National Laboratory Radiochemical Diagnostic Tracer Program. Several properties were desired for an alloy to be useful for tracer program applications. A suitable alloy would have a fairly high density, be ductile, homogeneous and easy to prepare. Alloys investigated have included uranium-americium, aluminum-americium, and cerium-americium. Uranium-americium alloys with the desired properties proved to be difficult to prepare, and work with this alloy was discontinued. Aluminum-americium alloys were much easier to prepare, but the alloy consisted of an aluminum-americium intermetallic compound (AmAl 4) in an aluminum matrix. This alloy could be cast and formed into shapes, but the low density of aluminum, and other problems, made the alloy unsuitable for the intended application. Americium metal was found to have a high solid solubility in cerium and alloys prepared from these two elements exhibited all of the properties desired for the tracer program application. Cerium-americium alloys containing up to 34 wt% americium have been prepared using both co-melting and co-reduction techniques. The latter technique involves co-reduction of cerium tetrafluoride and americium tetrafluoride with calcium metal in a sealed reduction vessel. Casting techniques have been developed for preparing up to eight 2.2 cm (0.87 in) diameter disks in a single casting, and cerium-americium metal alloy disks containing from 10 to 25 wt% 241Am have been prepared using these techniques.

AN OUTBREAK OF ACHROMOBACTER XYLOSOXIDANS RELATED TO DIAGNOSTIC TRACER PROCEDURES

In December, 1978, an investigation was undertaken to determine the source of infection in five patients in one hospital with hospital-associated bacteremia due to Achromobacter xylosoxidans. Review of their records showed that each had a diagnostic tracer procedure preceding the bacteremia and that no other procedures were common to all. Further investigation revealed that patients from three other hospitals were studied using diagnostic tracer materials from the index hospital. Five patients with confirmed A. xylosoxidans bacteremia and four suspected cases were identified in these hospitals, and all had a scan before the bacteremia was detected. No other A. xylosoxidans isolates were identified in any of the hospitals in the preceding two years. Although not confirmed, the source appeared to be stored non-bacteriostatic saline. Effective control measures included a sterility testing program and use of pre-packaged single dose vials of saline. Diagnostic tracer studies should be added to the list of procedures known to cause hospital-acquired bacteremias.

Organization of cardiovascular nuclear medicine units

Progress in the development of cardiovascular nuclear medicine can be accelerated by close cooperation between cardiologists and nuclear medicine physicians in the planning, performance and interpretation of diagnostic tracer studies. The special needs of patients with acute cardiovascular disorders often require supplementation of the hospital's central nuclear medical facility with one or more satellite units in or near the coronary care unit, cardiac operating suite, postoperative intensive care unit or emergency room. Newly emerging noninvasive cardiac diagnostic laboratories should be equipped to perform certain nuclear medicine procedures. Selected nuclear diagnostic procedures also can provide useful supplemental information during cardiac catheterization and angiography.

Carbohydrates as potential diagnostic tracers for brain tumors.

Currently available diagnostic tracers for brain tumors are not specific. Tumor-specific tracers would improve the detection of brain tumors by gamma encephalography. Glucose is an important substrate for tumor metabolism and is known to be taken up in large amounts. The authors have studied five labeled carbohydrates in an attempt to find a tumor-specific tracer: three were tritiated (L-galactose-1-3H, L-fucose-3H, and 4,6-dideoxy-xylo-hexose-3H) and two were radioiodinated (methyl-6-125I-6-deoxy-D-glucoside and 6-125I-6-deoxy-D-glucose). The uptake of these tracers by a transplantable mouse ependymoblastoma after intravenous injection was determined by liquid and well scintillation counting. The highest tumor-to-brain ratio was 7.1 to 1 for the tritiated tracers and 6.2 to 1 for the radioiodinated tracers. Although these ratios are not high enough for gamma encephalography, one of the iodinated tracers may be useful for enhancement of contrast in computerized axial tomography.

Distribution of Lysine Pathways Among Fungi: Evolutionary Implications

With the aid of diagnostic radiocarbon tracers, lysine synthesis was studied in representatives of 21 orders of basidiomycetes, ascomycetes, and phycomycetes. The labeling pattern corresponding to the α-aminoadipic acid-lysine path was given by all basidiomycetes and ascomycetes and by those phycomycetes which produce non-flagellate or posteriorly uniflagellate spores. The pattern characteristic of the α,ε-diaminopimelic acid-lysine path was shown by those phycomycetes which produce anteriorly uniflagellate or biflagellate spores. The remarkable consistency of the distribution of the two lysine paths suggests that (a) they did not arise sporadically; (b) their distribution pattern was not disturbed by genetic exchange; and (c) there is a substantial evolutionary gap in organisms differing in path of lysine synthesis. Neither lysine path is thought to have emerged in an organism possessing the other. The α,ε-diaminopimelic acid path may be the more ancient. A common evolutionary precursor of organisms having the α-aminoadipic acid path is postulated; these organisms include euglenids as the only non-fungal forms known to have this path. The inferred common precursor is viewed as a lysine-non-producing, animal-like organism in an evolutionary line that had branched off the main stream of evolution of the plant kingdom

Lysine Synthesis and Phytogeny of Lower Fungi : Some Chytrids versus Hyphochytrium

RECENT work, conducted with the aid of various diagnostic carbon-14 tracers, has suggested that lysine biosynthesis is a valuable character in the detection of certain evolutionary relationships1–4. All the eubacteria, pseudomonads, actinomycetes1, green algae2, and higher (vascular) plants3 examined appear to synthesize lysine in one general manner (presumably via α,ɛ-diaminopimelic acid, cf. ref. 5) and all the ascomycetous and basidiomycetous fungi1,3 (and also Euglena 2) in another (presumably via α-aminoadipic acid, cf. ref. 6). Among the lower fungi (phycomycetes), a striking dichotomous distribution of the two lysine paths was noted : the Mucorales and Blastocladiales studied, like the higher fungi, evidently use the path via α-aminoadipic acid, and the Saprolegniales that via α,ɛ-diaminopimelic acid4. The present communication reports findings with some other phycomycetes, including three chytrids and a representative of the Hyphochytriales. The latter group of organisms, although closely paralleling the chytrids in body structure, have uncertain phylogenetic affinities.