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Biomedical subjects

C Sagan

Publications and source records attributed to C Sagan.

At least 37 records · Page 2Linked to original sources
PubMed1997

Spontaneous dissection of the celiac artery.

We describe a case of intestinal angina caused by spontaneous dissection of the celiac artery and thrombosis of the superior mesenteric artery. Spontaneous dissection of a visceral artery is an uncommon occurrence that is usually diagnosed after fatal hemorrhage or ischemia. The underlying mechanism is unclear but the frequent association with multiple arterial lesions suggests general arterial disease. In symptomatic forms, surgical reconstruction is mandatory, to treat the lesion and allow definitive histological diagnosis.

Aortic Dissection↗
PubMed1997

[Management of differentiated thyroid cancer of nodular type].

Mortality and recurrence rate in nodular forms of differentiated thyroid cancer are 10 and 15%, raising the question of whether initial treatment was adequate. Recurrence and mortality appear to be higher after lobectomy than after total thyroidectomy. This could result from the development of dedifferentiated relapse or metastasis from residual areas. Metastatic node invasion is frequent (60 to 80%) but does not lead to a high recurrence rate. Prognosis is poor however due to frequent association with visceral metastases. Management should take into account the relative degree of malignancy of this cancer and the risk of morbidity for long surgical procedures. Lobectomy can be acceptable if no criteria of gravity is observed, but total thyroidectomy remains the treatment of choice. In patients with criteria of gravity, needle biopsy guides possible node dissection. Dissection of the recurrent chain misses 20% of the metastatic nodes, while dissection of the supraclavian and middle jugular recurrent chains only misses 7.8%. Radioactive iodine and hormone therapy are also indicated in patients with signs of gravity.

Adenocarcinoma, Follicular↗
PubMed1996

[Immunohistochemical study of 17 cases of rectal neuroendocrine tumors].

Seventeen rectal neuroendocrine tumors ("Rectal Carcinoids") were studied by immunohistochemistry using antibodies directed against neuroendocrine markers: chromogranin A, neuron-specific enolase, synaptophysin, neuroendocrine peptides (ACTH, glicentin, glucagon, pancreatic polypeptide, somatostatin, vasoactive intestinal peptide) and antibody against serotonin. All patients with tumors measuring 1 cm or less had no specific symptoms and survived between fifteen months and eight years. Only one patient with a 6 cm poorly differentiated neuroendocrine carcinoma died less than one year after diagnosis. Only five out of seventeen tumors secreted serotonin. Most tumors were derived from L cell secreting glucagon, glicentin or pancreatic polypeptide.

Adult↗
PubMed1996

[Combination of true and false left ventricular aneurysm. Cine-MRI diagnosis].

The authors report a case of a 68-year-old man with a history of postero-lateral myocardial infarction complicated by a true and a pseudo-aneurysm of the left ventricle, a chance finding during investigation of a systemic embolism. This is a rare association which is clinically difficult to diagnose. The authors describe the different complementary investigations available to make the diagnosis and underline the value of cine-MRI which was particularly useful in this case. Surgery may be indicated in cases of true aneurysm in cases with left ventricular failure but is mandatory in all cases of pseudo-aneurysm irrespective of the clinical presentation.

Aged↗
PubMed1996

[Oncocytic tumors of the thyroid. Diagnostic and therapeutic problems. Report of 17 cases and review of the literature].

Histopathologic and clinical follow-up data of 17 patients observed 3-104 months (mean: 38 months) after operation for oncocytic tumors of the thyroid gland are presented. Mean patient age was 50 +/- 15 years. Benign and malignant lesions were respectively 13 and 4. Frozen sections were positive for benign and malignant lesions in respectively 7 and 2 cases. Total thyroidectomy was performed in all cases of malignant lesions and in 7 cases of benign lesion, the latter in order to treat high volume adenomas or associated controlateral lesions. No tumor relapse was observed during the follow-up period (data about 16 patients). A review of the literature indicates that thyroid oncocytic adenoma diagnosis can be trusted and that this tumor is not especially prone to a malignant course with the mode of treatment applied. Thus total thyroidectomy should be recommended for: 1) malignant tumors. 2) and for selected benign adenomas depending on the tumor volume or on associated lesions.

Adenocarcinoma↗
PubMed1995

Galileo multispectral imaging of Earth.

Nearly 6000 multispectral images of Earth were acquired by the Galileo spacecraft during its two flybys. The Galileo images offer a unique perspective on our home planet through the spectral capability made possible by four narrowband near-infrared filters, intended for observations of methane in Jupiter's atmosphere, which are not incorporated in any of the currently operating Earth orbital remote sensing systems. Spectral variations due to mineralogy, vegetative cover, and condensed water are effectively mapped by the visible and near-infrared multispectral imagery, showing a wide variety of biological, meteorological, and geological phenomena. Global tectonic and volcanic processes are clearly illustrated by these images, providing a useful basis for comparative planetary geology. Differences between plant species are detected through the narrowband IR filters on Galileo, allowing regional measurements of variation in the "red edge" of chlorophyll and the depth of the 1-micrometer water band, which is diagnostic of leaf moisture content. Although evidence of life is widespread in the Galileo data set, only a single image (at approximately 2 km/pixel) shows geometrization plausibly attributable to our technical civilization. Water vapor can be uniquely imaged in the Galileo 0.73-micrometer band, permitting spectral discrimination of moist and dry clouds with otherwise similar albedo. Surface snow and ice can be readily distinguished from cloud cover by narrowband imaging within the sensitivity range of Galileo's silicon CCD camera. Ice grain size variations can be mapped using the weak H2O absorption at 1 micrometer, a technique which may find important applications in the exploration of the moons of Jupiter. The Galileo images have the potential to make unique contributions to Earth science in the areas of geological, meteorological and biological remote sensing, due to the inclusion of previously untried narrowband IR filters. The vast scale and near global coverage of the Galileo data set complements the higher-resolution data from Earth orbiting systems and may provide a valuable reference point for future studies of global change.

Africa↗
PubMed1995

Spectrophotometry and organic matter on Iapetus. 1. Composition models.

Iapetus shows a greater hemispheric albedo asymmetry than any other body in the solar system. Hapke scattering theory and optical constants measured in the laboratory are used to identify possible compositions for the dark material on the leading hemisphere of Iapetus. The materials considered are poly-HCN, kerogen, Murchison organic residue, Titan tholin, ice tholin, and water ice. Three-component mixtures of these materials are modeled in intraparticle, particle, and areal mixtures. In a computer grid search of approximately 2 x 10(7) models, an intraparticle mixture of 25% poly-HCN, 10% Murchison residue, and 65% water ice is found to best fit the spectrum, albedo, and phase behavior of the dark material. The Murchison residue and/or water ice can be replaced by kerogen and ice tholin, respectively, and still produce very good fits. Areal and particle mixtures of poly-HCN, Titan tholin, and either ice tholin or Murchison residue are also possible models. Poly-HCN is a necessary component in almost all good models. The presence of poly-HCN can be further tested by high-resolution observations near 4.5 micrometers.

Astronomy↗
PubMed1995

Tidal effects of disconnected hydrocarbon seas on Titan.

Thermodynamic and photochemical arguments suggest that Titan, the largest satellite of Saturn, has a deep ocean of liquid hydrocarbons. At visible wavelengths, Titan's surface is obscured by a thick stratospheric haze, but radar observations have revealed large regions of high surface reflectivity that are inconsistent with a global hydrocarbon ocean. Titan's surface has also been imaged at infrared wavelengths, and the highest-resolution data (obtained by the Hubble Space Telescope) show clear variations in surface albedo and/or topography. The natural interpretation of these observations is that Titan, like the Earth, has continents and oceans. But Titan's high orbital eccentricity poses a problem for this interpretation, as the effects of oceanic tidal friction would have circularized Titan's orbit for most configurations of oceans and continents. Here we argue that a more realistic topography, in which liquid hydrocarbons are confined to a number of disconnected seas or crater lakes, may satisfy both the dynamical and observational constraints.

Hydrocarbons↗
PubMed1995

Analytical pyrolysis experiments of Titan aerosol analogues in preparation for the Cassini Huygens mission.

Comparative pyrolysis mass spectrometric data of Titan aerosol analogues, called "tholins", are presented. The Titan tholins were produced in the laboratory at Cornell by irradiation of simulated Titan atmospheres with high energy electrons in plasma discharge. Mass-spectrometry measurements were performed at FOM of the solid phase of various tholins by Curie-point pyrolysis Gas-Chromatography/Mass-Spectrometry (GCMS) and by temperature resolved in source Pyrolysis Mass-Spectrometry to reveal the composition and evolution temperature of the dissociation products. The results presented here are used to further define the ACP (Aerosol Collector Pyrolyser)-GCMS experiment and provide a basis for modelling of aerosol composition on Titan and for the interpretation of Titan atmosphere data from the Huygens probe in the future.

Aerosols↗
PubMed1995

[Overexpression of protein p53 and Barrett esophagus. A frequent and early event in the course of carcinogenesis].

OBJECTIVES AND METHODS: In Barrett's oesophagus, the risk of malignancy is evaluated histologically with the presence of dysplasia. The abnormal expression of p53 protein could represent a useful new marker. The aim of this study was evaluate the abnormal expression of p53 protein in a series of 52 oesophagectomy specimens with Barrett's oesophagus, either non-dysplastic (n = 3), dysplastic (n = 8), or malignant (n = 41). The immunohistochemical study was made on deparaffinized sections with the monoclonal anti-p53 antibody DO7. RESULTS: The 3 non-dysplastic cases were p53 negative; 1 case of low-grade dysplasia in 5 was positive, as were the 3 cases of high grade dysplasia and 33 of 41 cancers (80%), including 13 superficial cancers in 14 (93%) and 20 invasive cancers in 27 (74%). A common feature was the presence of rare p53 positive crypts in low grade dysplastic areas and non-dysplastic specialized mucosa that surrounded high grade dysplasia and cancers. CONCLUSIONS: Our results confirm the high frequency of the abnormal expression of p53 protein in cancer developed in Barrett's oesophagus. This expression is a consequence of alterations of the TP53 gene, and has an important role in the carcinogenesis of Barrett's mucosa; it is likely to represent an early event. Prospective studies are needed to evaluate its interest in the surveillance of patients with Barrett's oesophagus.

Barrett Esophagus↗
PubMed1995

[Primary sclerosing cholangitis and systemic lupus erythematosus].

We report the association of primary sclerosing cholangitis and systemic lupus erythematosus in a 39 year-old man. Six months after a diagnosis of primary sclerosing cholangitis was established, the patient was hospitalized for a pleural effusion and acute pericarditis. Emergency pericardiocentesis, was required due to sudden cardiac tamponnade. Plasmatic anti-DNA and anti-nuclear antibodies were present. Treatment by steroids greatly improved symptoms. This clinical association suggests that some immune disorders may be common to the two diseases.

Adrenal Cortex Hormones↗
PubMed1995

[Horton disease of pulmonary localization].

A case of Horton's disease with interstitial pulmonary involvement is reported. Transbronchial biopsy of the lung and biopsy of the temporal artery provided evidence of giant cell lesions. Outcome was favourable with general corticosteroid therapy with regression of the pulmonary disease.

Aged↗
PubMed1994

The organic surface of 5145 Pholus: constraints set by scattering theory.

No known body in the Solar System has a spectrum redder than that of object 5145 Pholus. We use Hapke scattering theory and optical constants measured in this laboratory to examine the ability of mixtures of a number of organic solids and ices to reproduce the observed spectrum and phase variation. The primary materials considered are poly-HCN, kerogen, Murchison organic extract, Titan tholin, ice tholin, and water ice. In a computer grid search of over 10 million models, we find an intraparticle mixture of 15% Titan tholin, 10% poly-HCN, and 75% water ice with 10-micrometers particles to provide an excellent fit. Replacing water ice with ammonia ice improves the fits significantly while using a pure hydrocarbon tholin, Tholin alpha, instead of Titan tholin makes only modest improvements. All acceptable fits require Titan tholin or some comparable material to provide the steep slope in the visible, and poly-HCN or some comparable material to provide strong absorption in the near-infrared. A pure Titan tholin surface with 16-micrometers particles, as well as all acceptable Pholus models, fit the present spectrophotometric data for the transplutonian object 1992 QB1. The feasibility of gas-phase chemistry to generate material like Titan tholin on such small objects is examined. An irradiated transient atmosphere arising from sublimating ices may generate at most a few centimeters of tholin over the lifetime of the Solar System, but this is insignificant compared to the expected lag deposit of primordial contaminants left behind by the sublimating ice. Irradiation of subsurface N2/CH4 or NH3/CH4 ice by cosmic rays may generate approximately 20 cm of tholin in the upper 10 m of regolith in the same time scale but the identity of this tholin to its gas-phase equivalent has not been demonstrated.

Ammonia↗
PubMed1994

Chemical investigation of Titan and Triton tholins.

We report chromatographic and spectroscopic analyses of both Titan and Triton tholins, organic solids made from the plasma irradiation of 0.9:0.1 and 0.999:0.001 N2/CH4 gas mixtures, respectively. The lower CH4 mixing ratio leads to a nitrogen-richer tholin (N/C > 1), probably including nitrogen heterocyclic compounds. Unlike Titan tholin, bulk Triton tholin is poor in nitriles. From high-pressure liquid chromatography, ultraviolet and infrared spectroscopy, and molecular weight estimation by gel filtration chromatography, we conclude that (1) several H2O-soluble fractions, each with distinct UV and IR spectral signatures, are present, (2) these fractions are not identical in the two tholins, (3) the H2O-soluble fractions of Titan tholins do not contain significant amounts of nitriles, despite the major role of nitriles in bulk Titan tholin, and (4) the H2O-soluble fractions of both tholins are mainly molecules containing about 10 to 50 (C + N) atoms. We report yields of amino acids upon hydrolysis of Titan and Triton tholins. Titan tholin is largely insoluble in the putative hydrocarbon lakes or oceans on Titan, but can yield the H2O-soluble species investigated here upon contact with transient (e.g., impact-generated) liquid water.

Amino Acids↗
PubMed1994

The Titan haze revisited: magnetospheric energy sources and quantitative tholin yields.

We present laboratory measurements of the radiation yields of complex organic solids produced from N2/CH4 gas mixtures containing 10 or 0.1% CH4. These tholins are thought to resemble organic aerosols produced in the atmospheres of Titan, Pluto, and Triton. The tholin yields are large compared to the total yield of gaseous products: nominally, 13 (C + N)/100 eV for Titan tholin and 2.1 (C + N)/100 eV for Triton tholin. High-energy magnetospheric electrons responsible for tholin production represent a class distinct from the plasma electrons considered in models of Titan's airglow. Electrons with E > 20 keV provide an energy flux approximately 1 x 10(-2) erg cm-2 sec-1, implying from our measured tholin yields a mass flux of 0.5 to 4.0 x 10(-14) g cm-2 sec-1 of tholin. (The corresponding thickness of the tholin sedimentary column accumulated over 4 Gyr on Titan's surface is 4 to 30 m.) This figure is in agreement with required mass fluxes computed from recent radiative transfer and sedimentation models. If, however, these results, derived from experiments at approximately 2 mb, are applied to lower pressure levels toward peak auroral electron energy deposition and scaled with pressure as the gas-phase organic yields, the derived tholin mass flux is at least an order of magnitude less. We attribute this difference to the fact that tholin synthesis occurs well below the level of maximum electron energy deposition and to possible contributions to tholins from UV-derived C2-hydrocarbons. We conclude that Titan tholin, produced by magnetospheric electrons, is alone sufficient to supply at least a significant fraction of Titan's haze--a result consistent with the fact that the optical properties of Titan tholin, among all proposed materials, are best at reproducing Titan's geometric albedo spectrum from near UV to mid-IR in light-scattering models.

Aerosols↗
PubMed1994

Optical properties of poly-HCN and their astronomical applications.

Matthews (1992) has proposed that HCN "polymer" is ubiquitous in the solar system. We apply vacuum deposition and spectroscopic techniques previously used on synthetic organic heteropolymers (tholins), kerogens, and meteoritic organic residues to the measurement of the optical constants of poly-HCN in the wavelength range 0.05-40 micrometers. These measurements allow quantitative comparison with spectrophotometry of organic-rich bodies in the outer solar system. In a specific test of Matthews' hypothesis, poly-HCN fails to match the optical constants of the haze of the Saturnian moon, Titan, in the visible and near-infrared derived from astronomical observations and standard models of the Titan atmosphere. In contrast, a tholin produced from a simulated Titan atmosphere matches within the probable errors. Poly-HCN is much more N-rich than Titan tholin.

Astronomical Phenomena↗