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At least 1,153 records · Page 64Linked to original sources
PubMed1999

Prothiofos metabolites in human poisoning.

CASE REPORT: A 63-year-old woman was admitted to a local hospital after the ingestion of 40% prothiofos preparation (Tokuthion) 370 mL. Gastric lavage was performed and cathartics, active charcoal, diuretics, atropine sulfate, and pralidoxime were administered. Serum cholinesterase activity was 1.3 IU/L (normal 200-460 IU/L). The patient's consciousness was gradually restored after 4 hours of charcoal hemoperfusion and she was discharged 5 days after admission with no sequelae. METHOD: Plasma and urine prothiofos and metabolites were detected by gas chromatography-flame photometry and gas chromatography-mass spectrometry. Two despropyl metabolites were synthesized for identification and estimation. RESULTS: The main metabolites were identified with authentic prothiofos and methyl esters of synthesized des-S-propyl prothiofos oxon (O-2,4-dichlorophenyl O-ethyl phosphate), despropyl prothiofos oxon (O-2,4-dichlorophenyl O-ethyl phospholothiolate), and des-S-propyl prothiofos (O-2,4-dichlorophenyl O-ethyl phosphorothioate). Despropyl prothiofos (O-2,4-dichlorophenyl O-ethyl phosphorodithioate) was also identified in plasma. Large amounts of the hydrolyzed product, 2,4-dichlorophenol and its conjugate were also found. The metabolic pattern of prothiofos in humans appears to be different from that in rats.

Charcoal↗
PubMed2003

Purification of glutamate dehydrogenase isoenzymes and characterization of their substrate specificities.

Glutamate dehydrogenase (GDH) isoenzymes were purified from control, and ribonucleoside triphosphate (NTP)-treated peanut seedlings. GDH purification was by preparative-scale, free solution isoelectric focusing, followed by native PAGE, and the cryoelectrophoretic elution of the isoenzymes from the gel. SDS-PAGE of the purified GDH isoenzymes, followed by either silver staining of the gel, or western analysis using anti-GDH antibody, gave identical GDH polypeptide (a, alpha, and b) bands, thus, confirming the purity of the isoenzymes. The substrate specificities in the aminating activity of the GDH isoenzymes, or disaggregated polypeptides were determined by photometry, but the substrate specificities in the RNA synthesis activity were determined in cocktails containing 0.06-0.8 mM of each of UTP, ATP, GTP, and CTP, 0-100.0 mM NH4Cl, 0-50.0 mM alpha-ketoglutaratr (alpha-KG), 0-0.2 mM NADH, 0-10.0 mM CaCl2 5 units of DNase 1, antibiotics, and approximately 5 microg pure GDH isoenzymes or polypeptides at pH 8.0, and overnight at 16 degrees C. The GDH polypeptides were active only in amination reaction, but the GDH isoenzymes were active in both amination and RNA synthesis. Whereas, NADH, NH4Cl and alpha-KG served as the substrates for the amination reaction, and as modulators in the RNA synthetic reaction, ATP, GTP, UTP, and CTP served as substrates for theisoenzymes in RNA synthesis reaction. The product RNA was up to 2 microg microg(-1) GDH, and consisted of RNA species in the size ranges of 26, 16, and 5 S rRNAs. DNAse 1 in the assay cocktail ruled out transcription as the mechanism of the RNA synthesis. Addition of [alpha-32P] NTP led to the production of labeled RNA, thus confirming the specificity of NTPs as substrates, and that the RNA was not pre-existing in the reaction cocktail.

Arachis↗
PubMed1985

Structural organization of interphase 3T3 fibroblasts studied by total internal reflection fluorescence microscopy.

We studied the laminar organization of 3T3 fibroblast cells growing on glass slides by use of total internal reflection illumination to excite fluorescence emission (TIRF) from labeled molecules and stained cellular compartments that are very close to the cell-substrate contact region. Mitochondria, distant from the contact regions and stained with the water-soluble cationic dye, dil-C3-(3), fluoresced only as the glass/cytoplasm critical angle was approached. A similar result was obtained when the nuclei were stained with Hoechst dye 33342. From this measured angle a cytoplasmic refractive index in the range 1.358-1.374 was computed. The plasma membrane of 3T3 cells was stained with dil-C18-(3), and the cytoplasmic compartment was stained with fluoresceinyl-dextran (FTC-dextran) or with carboxyfluorescein. We have demonstrated a high degree of correspondence between the low-reflectance zones in the reflection interference image of a live cell and the TIRF images of both the plasma membrane and cytoplasmic compartment. TIRF photometry of selected contact regions of cells provided data from which the absolute separation of cell and substrate was computed. From a population of 3T3 cells microinjected with fluorescein-labeled actin, motile and adherent interphase cells were selected for study. For adherent cells, which displayed fluorescent stress fibers, the TIRF image was composed of intense patches and less intense regions that corresponded, respectively, to the focal contact and close-contact zones of the reflection-interference image. The intense patches corresponded to the endpoints of the stress fibers. Cells of motile morphology, which formed some focal contacts and extensive close-contact zones, gave AF-actin TIRF images of relatively even intensity. Thin lamellar regions of the cytoplasm were found to contain concentrations of actin not significantly different from other close-contact regions of the cell. The major analytical problem of TIRF microscopy is separation of the effects of proximity to substrate, refractive index, and fluorescent probe concentration on the local brightness of the TIRF image. From our results, it appears possible to use TIRF microscopy to measure the proximity of different components of substrate contact regions of cells.

Actins↗
PubMed1994

Yolk platelets in Xenopus oocytes maintain an acidic internal pH which may be essential for sodium accumulation.

Yolk platelets constitute an embryonic endocytic compartment that stores maternally synthesized nutrients. The pH of Xenopus yolk platelets, measured by photometry on whole oocytes which had endocytosed FITC-vitellogenin, was found to be acidic (around pH 5.6). Experiments on digitonin-permeabilized oocytes showed that acidification was due to the activity of an NEM- and bafilomycin A1-sensitive vacuolar proton-ATPase. Proton pumping required chloride, but was not influenced by potassium or sodium. Passive proton leakage was slow, probably due to the buffer capacity of the yolk, and was dependent on the presence of cytoplasmic monovalent cations. In particular, sodium could drive proton efflux through an amiloride-sensitive Na+/H+ exchanger. 8-Bromo-cyclic-AMP was found to increase acidification, suggesting that pH can be regulated by intracellular second messengers. The moderately acidic pH does not promote degradation of the yolk platelets, which in oocytes are stable for weeks, but it is likely to be required to maintain the integrity of these organelles. Furthermore, the pH gradient created by the proton pump, when coupled with the Na+/H+ exchanger, is probably responsible for the accumulation and storage of sodium into the yolk platelets during oogenesis.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1964

LABELLING OF DNA AND CELL DIVISION IN SO CALLED NON-DIVIDING TISSUES.

Autoradiographs of adult mice killed at various times after injection of tritiated thymidine show significant numbers of labelled nuclei in organs in which mitoses are either very rare or completely absent. The proportion of labelled cells that divide was estimated from the decline in the number of grains per nucleus, the number of pairs of labelled cells in sheets of epithelium in squashes, the number of labelled metaphases after 6 hours' treatment with Colcemid, and the ratio of mitotic index to labelling index. The longest possible duration of G(2) in the epithelial cells of seminal vesicles was deduced from the results of Feulgen photometry. The results show that only a small proportion of the labelled cells divide in the seminal vesicles and liver, whilst probably none divide in brain, smooth muscle, and heart muscle. It is suggested that, in the so called "non-dividing tissues" of adult mice, cells periodically renew their DNA by a process the details of which are as yet unknown.

Animals↗
PubMed1983

Regionalization and lateral diffusion of membrane proteins in unfertilized and fertilized mouse eggs.

The unfertilized mouse egg has a round and highly villated main body and a "nipple" that is unvillated and buds off on fertilization to form the second polar body. Fluorescent markers stain the body more intensely than the nipple, which has been assumed to result from surface amplification due to microvilli. Using fluorescence recovery after photobleaching and microfluorescence photometry, we have measured the membrane protein diffusion and concentration on the main body and nipple region of unfertilized and on fertilized CD-1 mouse eggs. Two general membrane protein labels were used: rhodamine-labeled succinylated concanavalin A and trinitrobenzene sulfonate visualized with a rhodamine Fab fragment of a sheep anti-trinitrophenyl. We found that while the diffusion coefficient was the same on the nipple and main body, considerably higher recovery was observed on the nipple for both probes. The ratio of intensity of fluorescence on the nipple to main body was significantly lower for the concanavalin A stain than for the trinitrophenyl stain, indicating that true concentration gradients exist beyond those that result from surface amplification. The effect of fertilization was not general. No effect was observed for the concanavalin A stain for either diffusion coefficient or percent recovery. For the trinitrophenyl stain, percent recovery decreased approximately twofold while diffusion coefficient increased approximately threefold.

Animals↗
PubMed1976

Nonuniform distribution of sodium in the rat hepatocyte.

The volume of the nucleus, endoplasmic reticulum (including Golgi complex), mitochondria, and cytoplasmic ground substance was measured in rat hepatocytes by stereological methods. The Na content was also measured by flame photometry. Variations in Na content correlated significantly with variations in volume of nucleus and endoplasmic reticulum. From the correlation parameters, Na concentrations were estimated as follows: nucleus, 108 mM; endoplasmic reticulum (ER) (including Golgie complex) 27 mM; cytoplasm (including and remaining organelles) 16 mM.

Animals↗
PubMed1987

Comet Sugano-Saigusa-Fujikawa (1983V)--a small, puzzling comet.

Spectroscopic and infrared observations of Comet Sugano-Saigusa-Fujikawa (1983V) were obtained during its close approach to the Earth on 11-14 June 1983. The [O I] production rates of 1.8 +/- 0.9 x 10(26) atoms/s observed on 12.3 June and 7 +/- 3.5 x 10(26) atoms/s on 13.4 June lead to derived water-production rates of 3 x 10(27) mol/s on 12 June and 1.1 x 10(28) mol/s on 13 June. The abundances of the minor species NH2, CN, C2, and C3 are unusually low relative to [O I]. The upper limit to the average nuclear radius from our infrared and visual photometry on 12-13 June (assuming that the entire signal came from the nucleus) is approximately 370 m. The dust/gas mass ratio was <0.01 on June 12 and <0.005 on June 13.

Astronomical Phenomena↗
PubMed1996

The 0.8 day orbit of the precataclysmic binary EUVE J1016-053.

The optical counterpart of the new extreme ultraviolet source EUVE J1016-053 (=RE 1016-053) is known to show intermittent sharp Balmer and HE I emission and traces of an M dwarf associated with a white dwarf optical spectrum. We present extensive optical spectroscopy showing the emission lines vary in velocity and intensity on a period of 0d.78929 +/- 0d.00003. The phase of the emission-line strengths lags that of the velocities by 0.237 +/- 0.013 cycle, consistent with the quarter-cycle offset expected if emission arises from the side of the secondary facing the hot white dwarf. EUVE J1016-053 is another example of an extreme ultraviolet illumination-effect binary, which only recently emerged from a common-envelope phase of binary evolution. Based on spectroscopic measurements and new BVR photometry, we find that the M dwarf secondary's contribution to the combined light is smaller than previously reported, probably because of the difficulty of avoiding contamination from a third star 3".2 distant. The velocity of the weak H II absorption is in antiphase to the emission, suggesting that it originates in the white dwarf photosphere. The mass function implied by the emission-line motion is f(M) = 0.28 +/- 0.08 M solar. Assuming the He II absorption does follow the white dwarf, the mass ratio MWD/MdM is 1.8 +/- 0.5, and the gravitational redshift is 45 +/- 14 km s-1. The modulation of the emission lines suggests the inclination i > 40 degrees, but plausible masses demand this inclination be well above the value.

Astronomical Phenomena↗
PubMed1999

Superhumps in a Peculiar SU Ursae Majoris-Type Dwarf Nova, ER Ursae Majoris.

We report the photometry of a peculiar SU Ursae Majoris-type dwarf nova, ER Ursae Majoris, for 10 nights during 1998 December and 1999 March, covering a complete rise to the supermaximum and a normal outburst cycle. Superhumps have been found during the rise to the superoutburst. A negative superhump appeared in the December 22 light curve, while the superhump on the next night became positive and had a large-amplitude waveform distinct from that of the previous night. In the normal outbursts we captured, superhumps with larger or smaller amplitudes seem to always exist, although it is not necessarily true for every normal outburst. These results show great resemblance to V1159 Ori. It is more likely that superhumps occasionally exist at essentially all phases of the eruption cycles of ER UMa stars, which should be considered in modeling.

Journal Article↗
PubMed2000

Clump Giant Distance to the Magellanic Clouds and Anomalous Colors in the Galactic Bulge.

I demonstrate that the two unexpected results in the local universe-(1) anomalous intrinsic (V-I&parr0;0 colors of the clump giants and RR Lyrae stars in the Galactic center, and (2) very short distances to the Magellanic Clouds (LMC, SMC) as inferred from clump giants-are connected with each other. The (V-I&parr0;0 anomaly is partially resolved by using the photometry from phase II of the Optical Gravitational Lensing Experiment (OGLE) rather than phase I. The need for V- or I-magnitude-based change in the bulge (V-I&parr0;0 is one option to explain the remaining color discrepancy. Such a change may originate in a coefficient of selective extinction AV&solm0;E&parl0;V-I&parr0; smaller than typically assumed. Application of the (V-I&parr0;0 correction (independent of its source) doubles the slope of the absolute magnitude-metallicity relation for clump giants, so that MI&parl0;RC&parr0;=-0.23+0.19 [Fe/H]. Consequently, the estimates of the clump distances to the LMC and SMC are affected. Udalski's distance modulus of µLMC=18.18+/-0.06 increases to 18.27+/-0.07. The distance modulus to the SMC increases by 0.12 to µSMC=18.77+/-0.08. I argue that a more comprehensive assessment of the metallicity effect on MI&parl0;RC&parr0; is needed.

Journal Article↗
PubMed2000

A Transiting "51 Peg-like" Planet.

Doppler measurements from Keck exhibit a sinusoidal periodicity in the velocities of the G0 dwarf HD 209458, having a semiamplitude of 81 m s-1 and a period of 3.5239 days, which is indicative of a "51 Peg-like" planet with a minimum mass (Msini) of 0.62 MJup and a semimajor axis of 0.046 AU. Follow-up photometry reveals a drop of 0.017 mag at the predicted time (within the errors) of transit by the companion based on the velocities. This is the first extrasolar planet observed to transit its star. The radius of the planet derived from the magnitude of the dimming is 1.42 RJup, which is consistent with models of irradiated Jupiter-mass planets. The transit implies that sini>0.993, leading to a true mass of 0.62 MJup for the planet. The resulting mean density of 0.27 g cm-3 implies that the companion is a gas giant.

Journal Article↗
PubMed2000

A Second Luminous Blue Variable in the Quintuplet Cluster.

H- and K-band moderate-resolution and 4 µm high-resolution spectra have been obtained for FMM 362, a bright star in the Quintuplet Cluster near the Galactic center. The spectral features in these bands closely match those of the Pistol Star, a luminous blue variable and one of the most luminous stars known. The new spectra and previously obtained photometry imply a very high luminosity for FMM 362, L>/=106 L middle dot in circle, and a temperature of 10,000-13,000 K. Based on its luminosity, temperature, photometric variability, and similarities to the Pistol Star, we conclude that FMM 362 is a luminous blue variable.

Journal Article↗
PubMed2000

Detection of Planetary Transits of the Star HD 209458 in the Hipparcos Data Set.

A search of the Hipparcos satellite photometry data for the star HD 209458 reveals evidence for a planetary transit signature consistent with the planetary properties reported by Henry et al. and Charbonneau et al. and allows further refinement of the planet's orbital period. The long time baseline (about 2926 days or 830 periods) from the best Hipparcos transit-like event to the latest transit reported by Henry et al. for the night of 1999 November 15 (UT) allows for an orbital period determination of 3.524736 days with an uncertainty of 0.000045 days (3.9 s). The transit events observed by Charbonneau et al. fall at the interim times expected to within the errors of this newly derived period. A series of statistical tests was performed to assess the likelihood of these events occurring by chance. This was crucial given the ill-conditioned problem presented by the sparse sampling of the light curve and the non-Gaussian distribution of the points. Monte Carlo simulations using bootstrap methods with the actual Hipparcos HD 209458 data set indicate that the transit-like signals of the depth observed would only be produced by chance in 21 out of 1 million trials. The transit durations and depths obtained from the Hipparcos data are also consistent with those determined by Charbonneau et al. and Henry et al. within the limitations of the sampling intervals and photometric precision of the Hipparcos data.

Journal Article↗
PubMed2000

2 Micron Spectroscopy within 0&farcs;3 of Sagittarius A*

We present moderate- (R approximately 2700) and high-resolution (R approximately 22,400) 2.0-2.4 µm spectroscopy of the central 0.1 arcsec2 of the Galaxy obtained with the facility near-infrared spectrometer (NIRSPEC) for the Keck II telescope. The composite spectra do not have any features attributable to the brightest stars in the central cluster; i.e., after background subtraction, W12CO&parl0;2-0&parr0;<2 Å. This stringent limit leads us to conclude that the majority, if not all, of the stars are hotter than typical red giants. Coupled with previously reported photometry, we conclude that the sources are likely OB main-sequence stars. In addition, the continuum slope in the composite spectrum is bluer than that of a red giant and is similar to that of the nearby hot star IRS 16NW. It is unlikely that they are late-type giants stripped of their outer envelopes because such sources would be much fainter than those observed. Given their inferred youth (tauage<20 Myr), we suggest the possibility that the stars have formed within 0.1 pc of the supermassive black hole. We find a newly identified broad-line component (VFWHM approximately 1000 km s-1) toward the 2.2178 µm [Fe iii] line located within a few arcseconds of Sagittarius A*. A similar component is not seen in the Brgamma emission.

Journal Article↗
PubMed2000

New Evidence for the Complex Structure of the Red Giant Branch in omega Centauri.

We report on the complex structure of the red giant branch (RGB) of omega Centauri, based on a new wide-field and wide-color baseline B and I photometry. Our color-magnitude diagram (CMD) shows the presence of multiple populations along this branch; in particular, we discovered an anomalous branch (RGB-a), which appears to be well separated from the bulk of the RGB stars. On the basis of our CMD and from the previous literature, we conclude that (1) these stars, clearly identified as a separate population in our CMD, represent the extreme metal-rich extension (&sqbl0;Ca&solm0;H&sqbr0;>-0.3) of the stellar content of omega Cen and show anomalous abundances of s-process elements (as Ba and Zr) as well; (2) they are physical members of the omega Cen system; (3) they comprise approximately 5% of the stars of the whole system; and (4) this component and the metal intermediate one (-0.4>&sqbl0;Ca&solm0;H&sqbr0;>-1) have been found to share the same spatial distribution, both of them differing significantly from the most metal-poor one (&sqbl0;Ca&solm0;H&sqbr0;<-1). This last piece evidence supports the hypothesis that metal-rich components could belong to an independent (proto?) stellar system captured in the past by omega Cen.

Journal Article↗
PubMed2000

Dust Echoes from Gamma-Ray Bursts.

The deviation from the power-law decline of the optical flux observed in GRB 970228 and GRB 980326 has been used recently to argue in favor of the connection between gamma-ray bursts and supernovae. We consider an alternative explanation for this phenomenon, based on the scattering of a prompt optical burst by 0.1 M middle dot in circle dust located beyond its sublimation radius 0.1-1 pc from the burst. In both cases, the optical energy observed at the time of the first detection of the afterglow suffices to produce an echo after approximately 20-30 days, as observed. Prompt optical monitoring of future bursts and multiband photometry of the afterglows will enable us to test simple models of dust reprocessing quantitatively and to predict source redshift.

Journal Article↗
PubMed2000

Deficiency of "Thin" Stellar Bars in Seyfert Host Galaxies.

Using all available major samples of Seyfert galaxies and their corresponding closely matched control samples of nonactive galaxies, we find that the bar ellipticities (or axial ratios) in Seyfert galaxies are systematically different from those in nonactive galaxies. Overall, there is a deficiency of bars with large ellipticities (i.e., "thin" or "strong" bars) in Seyfert galaxies compared to nonactive galaxies. Accompanied with a large dispersion due to small number statistics, this effect is strictly speaking at the 2 sigma level. To obtain this result, the active galaxy samples of near-infrared surface photometry were matched to those of normal galaxies in type, host galaxy ellipticity, absolute magnitude, and, to some extent, redshift. We discuss possible theoretical explanations of this phenomenon within the framework of galactic evolution, and, in particular, of radial gas redistribution in barred galaxies. Our conclusions provide further evidence that Seyfert hosts differ systematically from their nonactive counterparts on scales of a few kiloparsecs.

Journal Article↗