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  • Articles  (80)
  • Springer  (56)
  • Wiley  (22)
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  • Geological Society of America (GSA)
  • Periodicals Archive Online (PAO)
  • 2000-2004  (14)
  • 1995-1999  (47)
  • 1980-1984  (19)
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  • Medicine  (79)
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  • Articles  (80)
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  • 1
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned fibre preparations from the extensor digitorum longus muscle of the rat were used to test whether a rise in myoplasmic [NH4 +] in the range 2–10 mm interferes with the mechanism of excitation-contraction coupling in fast-twitch mammalian muscle. Under our conditions (pH 7.10, Mg2+ 1 mm, temperature 23° C), [NH4 +] up to 10 mm had little effect on the Ca+-activated force and on the peak of the t-system depolarization-induced force response. However, the duration of the depolarization-induced force response was decreased significantly at [NH4 +] ≥2 mm. From these data we conclude that the intracellular accumulation of NH4 + is not likely to play a major role in fatigue. Nevertheless, the build up of NH4 + during fatigue, may have a significant inhibitory effect on the force output by decreasing the duration of the t-system depolarization-induced activation of the contractile apparatus.
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  • 2
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The main objective of this study was to analyse glycogen in single muscle fibres, using a recently developed microfluorometric method which detects subpicomol amounts of NADPH, glucose and glycogen (as glucosyl units) (detection limit 0.16–0.17pmol in a 25nl sample) without fluorochrome amplification. The fibres were freshly dissected from the twitch region of the iliofibularis muscle of the cane toad (Bufo marinus), and were mechanically skinned under paraffin oil to gain access to the intracellular compartments. The results show that: (1) glycogen concentrations in toad skeletal muscle fibres range between 25.8 and 369mmol glucosyl units/litre fibre volume; (2) there is a large variation in glycogen content between individual fibres from the iliofibularis muscle of one animal; (3) there are seasonal differences in the glycogen content of toad single muscle fibres; (4) the total amount of glycogen in single muscle fibres of the toad does not decrease significantly when storing the tissue, under paraffin oil, at 20–25°C for up to 6h or at 4°C for up to 24h; and (5) 15–26% of fibre glycogen can be washed in an aqueous solution at pH 5–7, within 5min, while 74–85% of fibre glycogen remains associated with the washed skinned fibre, even after 40min exposure of the skinned fibre preparation to the aqueous environment. The retention of most glycogen in the fibre preparation after mechanical removal of the plasma membrane and extensive washing indicates that in toad skeletal muscle fibres the largest proportion of glycogen is tightly bound to intracellular structures. The results also show that the skinned muscle fibre preparation is well suited for microfluorometric glycogen determination, since low molecular weight non-glycogen contributors to the fluorescence signal can be removed from the myoplasmic space prior to the glycogen hydrolysis step.
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  • 3
    ISSN: 1435-604X
    Keywords: Keywords: Adenocarcinoma; Aminolaevulinic acid; Barrett's oesophagus; Dysplasia; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . Photodynamic therapy (PDT) may have a role in the prevention of oesophageal cancer. Ten patients with Barrett's oesophagus, three with low-grade dysplasia (LGD), four with high-grade dysplasia (HGD), one with carcinoma in situ and two with invasive carcinoma, were treated with PDT. All received 30 mg/kg aminolaevulinic acid (ALA) followed 4 h later by laser endoscopy. Half were treated with red light (630 nm; 100 mW/cm2 for 1000 s) and half with green light (514 nm; 100 mW/cm2 for 500 s). Columnar epithelial regression was seen in all patients with dysplasia (mean area decrease 44%; range 10–100%), with apparent elimination of dysplasia in all cases. In patients with in situ or invasive carcinoma, no response was seen. ALA-induced PDT, using either red or green light, produces effective ablation of dysplastic Barrett's oesophagus, hence may have a role in the prevention of oesophageal carcinoma, but has little effect on in situ or invasive adenocarcinoma.
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  • 4
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Reductions of oxygen in inspired gas from 20% to 15%, in anesthetized dogs, reduced arterial PO2 and increased the renal efflux of PGE2 but not PGF2a . Renal blood flow, blood pressure, plasma renin activity as well as arterial pH and PCO2 were unaffected. PGs may mediate the renal hemodynamic or excretory consequences of alterations in PO2. In addition, minor variations in PO2 might account, in part, for the variable renal venous PGE2 concentrations reported under basal conditions.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 31 (1983), S. 459-466 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 29 (1995), S. 344-350 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The acute toxicity (96-h LC50) of aqueous stable iodine species (I−, IO 3 − , I2) to rainbow trout and Daphnia magna were measured at three individual concentrations of hardness, total organic carbon, and chloride. Rainbow trout were most sensitive to I2 (LC50⩾0.53 mg/L), and much less sensitive to IO 3 − (LC50⩾220 mg/L) or I− (LC50⩾860 mg/L). Daphnia magna were equally sensitive to I2 (LC50⩾0.16 mg/L) and I− (LC50⩾0.17 mg/L), but were less sensitive to IO 3 − (LC50⩾10.3 mg/L). The external and internal radiological dose imparted by equivalent molar quantities of radioactive 125I, 129I, and 131I were calculated for both the Daphnia and trout using the LC50 values obtained from a standard water treatment. As expected, the dose from 125I and 131I would exceed the expected lethal dose rate long before a chemically toxic level is reached. In contrast, a molar concentration of 129I likely to cause death by chemical toxicity would impart a radiological dose less than that expected to be lethal. Thus, for short-lived aquatic organisms, risks due to chemical toxicity of 129I may exceed risks due to its radioactive emissions.
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  • 7
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in storm water collected from 15 outfalls in San Francisco Bay, California, considered representative of areas located adjacent to petroleum refineries and mixed urban/commercial/residential land uses. Storm water sampling was conducted hourly over a 12-h period at two outfalls located near the city of Oakland and the suburban community of Benicia, which represent urban and mixed urban/light industrial land uses, respectively. Sampling was conducted hourly to determine temporal changes in the concentrations and distributions of PCDD/Fs during the first major rainstorm event of the 1995/96 winter season. In addition, storm water sampling was conducted in December 1995 and February/April 1996 at six publicly owned treatment work (POTW) outfalls located adjacent to developed, undeveloped, mixed residential/commercial, and industrial lands. Storm water sampling also was conducted at five outfalls located adjacent to petroleum refineries. The sampling results were used to examine changes in PCDD/F loadings to San Francisco Bay at the onset and midway through the winter rainy season and to characterize differences in PCDD/F concentrations, if any, between refinery and nonrefinery areas. The concentrations of tetra- through octa-chlorinated homologues and 2,3,7,8-substituted congeners were assayed in filtered storm water samples according to US EPA Method 1613A. Principal components analysis (PCA) was used as an exploratory technique to examine the similarities and differences in the distributions of PCDD/Fs in storm water from different outfalls. The sampling results showed few significant differences between storm water discharged from outfalls located in mixed urban/commercial/residential areas and outfalls located adjacent to petroleum refineries. The concentrations of 2,3,7,8-TCDD were below the analytical limits of detection in all storm water samples, with the exception of samples collected after the sixth hour of sampling at the Oakland outfall. Fingerprint patterns were generally dominated by the higher chlorinated PCDD/F congeners including OCDD, OCDF, and 1,2,3,4,6,7,8-HpCDD. Total TEQs were generally below US EPA ambient water quality criteria and aquatic ecotoxicology guideline values. The results of this study strongly suggest that discrete sampling of storm water outfalls is insufficient to characterize the concentrations and distributions of persistent hydrophobic contaminants such as PCDD/Fs. In addition to surface water runoff from the city of Oakland, other nonindustrialized urban locations may represent important sources of PCDD/Fs to San Francisco Bay.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 13 (1984), S. 313-326 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The use of small (1 m3) enclosures for providing data on the persistence and effects of chemicals in freshwater was investigated. The enclosures included an intact water column with its associated flora and fauna and provided water/air and water/sediment interfaces when placed in small ponds. The enclosures provided a means of examining a variety of toxic effects of two chemicals, an insecticide (methyl parathion) and a herbicide (linuron), under relatively natural conditions in a replicated experiment which lasted six weeks. Toxic effects on Zooplankton, macroinvertebrates, and the flora of the enclosures were observed and compared with the results of laboratory toxicity tests and bioassays of water samples collected from the enclosures. The persistence of the two chemicals in the water in the enclosures was followed by chemical analysis and bioassay. Experiments in enclosures could play a role in providing data to be used in the assessment of the hazard posed by chemicals: particularly in cases where the laboratory data on acute toxicity, to single species or simple associations of species, and knowledge of simple physical constants are inadequate to allow assessment of the hazard.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 28 (1995), S. 443-450 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The California State Mussel Watch program is a long-term monitoring program conducted by the State Water Resources Control Board and the Department of Fish and Game. In a fifteen year time span, from 1977–1992, mussels were collected at 378 stations. From these stations, 47 were chosen to conduct statistical analysis based on the criteria that they had been sampled at least 6 times for total DDTs, total polychlorinated biphenyls (PCBs), and total chlordanes. Declines of total DDTs and chlordanes were noted at approximately half of the stations. Declines of total PCBs were noted at approximately one-quarter of the stations. Declines of PCBs but not DDTs in mussels near Los Angeles County's sewer discharge corresponded to declines of these contaminants in treated effluent.
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  • 10
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In situ hybridization experiments on mitotic and lampbrush chromosomes show that histone genes and an associated 222 bp repeated sequence, satellite 1, are located at or near the sphere loci of chromosomes 2 and 6 of the newt Notophthalmus viridescens. During the lampbrush chromosome stage, transcripts of the histone genes and of satellite 1 occur on loops associated with the spheres. Histone genes are located at sites on the mitotic chromosomes of Triturus cristatus and T. alpestris which are consistent with the known positions of spheres on their lampbrush chromosomes.
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