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At least 1,135 records · Page 63Linked to original sources
PubMed1998

Atmospheric radiocarbon calibration to 45,000 yr B.P.: late glacial fluctuations and cosmogenic isotope production

More than 250 carbon-14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from Lake Suigetsu (Japan) provide a first atmospheric calibration for almost the total range of the radiocarbon method (45,000 years before the present). The results confirm the (recently revised) floating German pine chronology and are consistent with data from European and marine varved sediments, and combined uranium-thorium and carbon-14 dating of corals up to the Last Glacial Maximum. The data during the Glacial show large fluctuations in the atmospheric carbon-14 content, related to changes in global environment and in cosmogenic isotope production.

Journal Article↗
PubMed1998

Deep-Sea coral evidence for rapid change in ventilation of the deep north atlantic 15,400 years Ago

Coupled radiocarbon and thorium-230 dates from benthic coral species reveal that the ventilation rate of the North Atlantic upper deep water varied greatly during the last deglaciation. Radiocarbon ages in several corals of the same age, 15.41 +/- 0.17 thousand years, and nearly the same depth, 1800 meters, in the western North Atlantic Ocean increased by as much as 670 years during the 30- to 160-year life spans of the samples. Cadmium/calcium ratios in one coral imply that the nutrient content of these deep waters also increased. Our data show that the deep ocean changed on decadal-centennial time scales during rapid changes in the surface ocean and the atmosphere.

Journal Article↗
PubMed1998

Climate and vegetation history of the midcontinent from 75 to 25 ka: A speleothem record from crevice cave, missouri, USA

Four Missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago (ka). The thorium-230-dated records reveal that between 75 and 55 ka, the midcontinental climate oscillated on millennial time scales between cold and warm, and vegetation alternated among forest, savanna, and prairie. Temperatures were highest and prairie vegetation peaked between 59 and 55 ka. Climate cooled and forest replaced grassland at 55 ka, when global ice sheets began to build during the early part of Marine Oxygen Isotope Stage 3.

Journal Article↗
PubMed1999

Evolution of the continents and the atmosphere inferred from Th-U-Nb systematics of the depleted mantle

Temporal evolution of depleted mantle thorium-uranium-niobium systematics constrain the amount of continental crust present through Earth's history (through the niobium/thorium ratio) and date formation of a globally oxidizing atmosphere and hydrosphere at approximately 2.0 billion years ago (through the niobium/uranium ratio). Increase in the niobium/thorium ratio shows involvement of hydrated lithosphere in differentiation of Earth since approximately 3.8 billion years ago. After approximately 2.0 billion years ago, the decreasing mantle thorium/uranium ratio portrays mainly preferential recycling of uranium in an oxidizing atmosphere and hydrosphere. Net growth rate of continental crust has varied over time, and continents are still growing today.

Journal Article↗
PubMed1983

Lysosomal response of a murine macrophage-like cell line persistently infected with Coxiella burnetii.

The lysosomal response of a murine macrophage-like tumor cell line (J774) during persistent infection with Coxiella burnettii was examined. By using acid phosphatase as a lysosomal marker, it was shown that phagosome-lysosome fusion occurred in J774 cells persistently infected with C. burnetii. This observation was verified using thorium dioxide, an electron-dense compound that is sequestered in secondary lysosomes. The phagolysosomes contained viable replicating rickettsiae. Spectrofluorometric analysis indicated that the phagolysosomal pH of persistently infected cells was acidic. In attempts to correlate rickettsial survival with lysosome function, the activities of several lysosomal enzymes were assayed in both infected and uninfected cells. Activities of acid phosphatase and beta-acetylglucosaminidase were not significantly altered during infection. However, infected cells appeared to display slightly higher intracellular lysozyme, beta-glucuronidase, and beta-galactosidase activities.

Acid Phosphatase↗
PubMed1984

Yersinia pestis grows within phagolysosomes in mouse peritoneal macrophages.

Transmission electron microscopy was used to determine the intracellular localization of Yersinia pestis growing within cultured resident peritoneal macrophages of mice. Monolayers fixed immediately, or as long as 4.5 h, after infection contained yersiniae closely surrounded by a membrane. The vesicles containing the yersiniae were determined to be phagolysosomes by labeling secondary lysosomes of macrophages with electron-dense particles of thorium dioxide. The presence of the label within vesicles containing yersiniae indicates that this pathogen grows within the lysosomal compartment of its target host cell.

Animals↗
PubMed2000

Coxiella burnetii exhibits morphological change and delays phagolysosomal fusion after internalization by J774A.1 cells.

Coxiella burnetii, the etiological agent of Q fever, is an obligate intracellular bacterium proliferating within the harsh environment of the phagolysosome. Mechanisms controlling trafficking to, and survival of pathogens within, the phagolysosome are unknown. Two distinct morphological variants have been implicated as playing a role in C. burnetii survival. The dormant small-cell variant (SCV) is resistant to extracellular stresses and the more metabolically active large-cell variant (LCV) is sensitive to environmental stresses. To document changes in the ratio of SCVs to LCVs in response to environment, a protein specific to SCV, ScvA, was quantitated. During the first 2 h after internalization of C. burnetii by J774A.1 cells, the level of ScvA decreased, indicating a change from a population containing primarily SCVs to one containing primarily LCVs. In vitro experiments showed that 2 h of incubation at pH 5.5 caused a significant decrease in ScvA in contrast to incubation at pH 4.5. Measuring in vitro internalization of [(35)S]methionine-[(35)S]cysteine in response to pH, we found the uptake to be optimal at pH 5.5. To explore the possibility that after uptake C. burnetii was able to delay phagolysosomal fusion, we used thorium dioxide and acid phosphatase to label phagolysosomes during infection of J774A.1 cells. We determined that viable C. burnetii was able to delay phagolysosomal fusion. This is the first time that a delay in phagolysosomal fusion has been shown to be a part of the infection process of this pathogenic microorganism.

Animals↗
PubMed1980

Angiosarcoma of the liver: annual occurrence and aetiology in Great Britain.

The annual occurrence of angiosarcoma of the liver (ASL) in Britain from 1963 to 1977 was studied, including clinical and occupational details for those cases agreed as ASL by a panel of histopathologists. Thirty-five cases (28 men, six women, and one infant girl) were agreed as ASL. The increase in the incidence of ASL observed in recent years was attributable to Thorotrast (thorium dioxide) usage (eight cases) and exposure to vinyl chloride (two cases) in the past. In its clinical presentation and prognosis ASL resembled primary liver carcinoma, except that extrahepatic metastases were found in only eight (23%) cases, and haemoperitoneum ws more common in those cases due to Thorotrast. The results suggested a possible increased risk of ASL in the electrical and plastics fabrication industries, but information on exposure was inadequate to implicate specific chemicals. The clinical features of one case were indicative of arsenical intoxication, but medications in the other patients did not appear to be of aetiological importance.

Adult↗
PubMed1994

Malignant vascular tumors of the liver: radiologic-pathologic correlation.

Although benign vascular tumors of the liver are extremely common (hemangioma is the most common), malignant vascular tumors of the liver are very rare. In the adult, these tumors are angiosarcoma, epithelioid hemangioendothelioma, and Kaposi sarcoma. All hepatic malignant vascular tumors share histologic characteristics, grow around and into vessels, and are grossly multifocal. They may be misdiagnosed histologically, particularly if only a biopsy sample is available. Although imaging findings are often non-specific, some features are suggestive or even characteristic of these neoplasms. Such features include previous exposure to thorium dioxide (Thorotrast) in cases of angiosarcoma, coalescence of multiple nodules into large peripheral masses in epithelioid hemangioendothelioma, and association between acquired immunodeficiency syndrome and cutaneous involvement in Kaposi sarcoma. Because hepatic malignant vascular tumors are often multiple, the main differential diagnosis is metastatic disease. There is no effective treatment for these tumors, and although survival time is variable, the prognosis is generally unfavorable.

Hemangioendothelioma, Epithelioid↗
PubMed1988

Intrahepatic cholangiocarcinoma: radiologic-pathologic correlation.

Seventeen proved cases of intrahepatic cholangiocarcinoma (ICAC) were reviewed to establish a radiologic-pathologic correlation. The most common appearance of ICAC at computed tomography (CT) is that of a single, homogeneous low-attenuation mass. Multiple low-attenuation lesions were present in four cases. Calcification was depicted by CT in three cases. At angiography, ICAC has a variable appearance with avascular, hypovascular, and hypervascular patterns possible. Portal obstruction was seen in only one case. The most common appearance of ICAC at sonography is that of a homogeneously hyperechoic mass, either single or multiple. In only one case was ICAC hypoechoic. Plain abdominal radiography demonstrated calcification in three patients and evidence of Thorotrast (thorium dioxide) deposition in one. Upper gastrointestinal series demonstrated abnormal gastric folds in two cases, corresponding to gastric invasion by ICAC. There were no characteristic radiographic findings, but the following features may be helpful in differentiating ICAC from other primary intrahepatic tumors, particularly typical hepatocellular carcinoma: a homogeneously echogenic or high-attenuation appearance on images that reflects the uniform nature observed at pathologic examination, the presence of calcification, and the uncommon invasion of portal or hepatic veins. Conversely, the presence of satellite lesions may blur the the distinction between ICAC and metastatic liver disease.

Adenoma, Bile Duct↗
PubMed1980

Polysaccharidic material in chloride cell of teleostean gill: modifications according to salinity.

The gill epithelium is known to be implicated in the hydromineral regulation of teleosts, especially owing to its "chloride cells." We have examined the polysaccharides of chloride cells from euryhaline teleosts adapted to fresh- or saltwater. The use of periodic acid-chromic acid-silver methenamine, colloidal thorium, or radioautography after incorporation of [3H]glucosamine has shown that chloride cells are characterized by a high concentration of polysaccharides in their apical region (at the level of the vesiculotubular system) and by a special polysaccharidic cell coat. The polysaccharide molecules originate from the Golgi area; by 12 h they accumulate within the vesiculotubular system and are released in the apical cavity of the cell within 24 h. In fresh- and saltwater-adapted fish, the localization of polysaccharidic material in chloride cells is basically the same. However, in saltwater-adapted fish, the amount and turnover of the polysaccharide molecules are clearly increased.

Adaptation, Physiological↗
PubMed1979

Scanning electron microscopy in the evaluation of neurosurgical neoplasms: a review of new approaches.

Present and potential applications of scanning electron microscopy (SEM) to the study of solid neoplasms, the lining of cysts, exfoliated cells, mineral deposits, and supporting tissues of the central nervous system (CNS) are discussed. Special features of the SEM image include a large field of view and depth of focus, high resolution, and a three-dimensional impression of surface topography. These features have contributed a clearer understanding of similarities between colloid cyst and olfactory epithelium. They demonstrated differences between glial and nonglial fibrils of selected CNS neoplasms. These features may ultimately enhance decisions, diagnosis, and study of neoplastic origins and spread within the CNS and cerebrospinal fluid. Special features of tissue examination by SEM include processing without the need of thin sections and elemental analysis by X-ray spectroscopy. These features have been applied to studies of calcium and thorium associated with meningiomas and a schwannoma.

Adenoma↗
PubMed2002

Removal and recovery of uranyl ion using various microorganisms.

The adsorption of uranyl ion by microorganisms was examined. Among the 76 strains of 69 species tested (23 bacteria, 20 actinomycetes, 18 fungi, and 15 yeasts), high uranyl ion adsorption ability was exhibited by strains of the bacteria, Arthrobacter nicotianae, Bacillus subtilis, and Micrococcus luteus. A. nicotianae cells, which showed the best performance, could adsorb about 698 mg uranyl ion (2.58 mmol) per gram dry wt. of microbial cells. The adsorption of uranyl ion was rapid, selective, and mostly dependent on physico-chemical binding to the cell components. As well as uranyl ion, A. nicotianae could adsorb thorium ion with high efficiency. Cells immobilized with polyacrylamide gel could be used during repeated adsorption-desorption cycles.

Journal Article↗
PubMed2005

Indirect determination of uranium by the on-line reduction and fluorimetric detection of cerium(III).

A novel flow injection method has been developed for the indirect determination of uranium by the on-line reduction and subsequent fluorimetric detection of cerium(III). A sample solution containing uranium(VI), prepared as a sulfuric acid solution, was injected into a sulfuric acid carrier solution and passed through a column packed with metal bismuth to reduce uranium(VI) to uranium(IV). The sample solution was merged with a cerium(IV) solution to oxidize uranium(IV) to uranium(VI) and the cerium(III) generated was then monitored fluorimetricaly. The present method is free from interference from zirconium, lanthanides, and thorium, and has been successfully applied to the determination of uranium in monazite coupled with an anion-exchange separation in a sulfuric acid medium to eliminate iron(III). The sample throughput was 25 per hour and the lowest detectable concentration was 0.0042 mg l(-1).

Journal Article↗
PubMed1978

The effect of ischaemia on the function and fine structure of the microvasculature of myocardium.

Seventeen mongrel dogs were subjected to ligation of the circumflex branch of the left coronary artery. At intervals from 10 to 300 minutes after ligation, 10 ml of a sodium fluorescein and colloidal thorium hydroxide solution were injected via an intra-arterial catheter placed distal to the ligature. Up to 20 minutes after ligation this tracer solution evenly perfused the left ventricular wall including the posterior papillary muscle (PPM). During 25 to 50 minutes there was a progressive patchy loss of perfusion into the PPM although the sub-epicardial region was evenly perfused. After 60 or more minutes of ischaemia it was not possible to inject this tracer solution into the subendocardial region. Electron microscopic examination indicated that this loss of vascular competence was possibly due to vasospasm of some vessels in the marginal zone between the perfused and non-perfused areas and was unlikely to be due to intravascular thrombosis, endothelial cell swelling, or to compression of vessels due to cell or tissue oedema.

Animals↗
PubMed1995

Physiological and toxicological changes in the skin resulting from the action and interaction of metal ions.

The human environment contains more than 50 metal or metalloid elements. At least 15 are recognized as trace elements, with zinc, calcium, copper, magnesium, and iron having specific roles in skin morphogenesis and function. The present review focuses on the presumed role of metal ions in the skin, their competition for carrier proteins, and membrane receptors. Evidence presented shows that the balance of trace metal ions is critical for normal skin and repair mechanisms following injury. Xenobiotic ions can impair this balance, leading to pathological change. The skin acts as an organ of elimination of excess trace metals and xenobiotic ions from the body, but mechanisms of voidance vary for different metals. Metal ions are an important cause of allergies, and evidence is presented to show that the majority of metals or metal compounds can induce allergic changes. Except for chromium and nickel, which are among the most common human allergens, animal models have provided little information. At least cadmium, thorium, lead, chromium, nickel, beryllium, and arsenic and proven or putative carcinogens in animals or humans on the basis of cytological or epidemiological evidence. However, only arsenic exhibits a clear predilection for the skin. Other metals such as gold can induce subcutaneous sarcoma following injection, but the relevance of this observation in terms of human occupational risk is discounted.

Animals↗
PubMed1984

[Studies on background radioactivity in the Niigata City area--identification of natural nuclides present in underground (well) water samples].

Background radioactivity levels in Niigata city area were studied through the years of 1981-1984. As the results, it was found that the gross beta-radioactivity in underground (well) water samples were comparatively higher than those of other ground water samples. Ion chromatographic and gamma-ray spectroscopic determination revealed that this higher radioactivities were contributed by 40K rather than radium or thorium series nuclides or fallout originated 90Sr.

Background Radiation↗