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  • 1995-1999  (3)
  • 1970-1974  (3)
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  • 1
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In support of the spiral wave theory of reentry, simulation studies and animal models have been utilized to show various patterns of spiral wave tip motion such as meandering and drifting. However, the demonstration of these or any other patterns in cardiac tissues have been limited. Whether such patterns of spiral tip motion are commonly observed in fibrillating cardiac tissues is unknown, and whether such patterns form the basis of ventricular tachycardia or fibrillation remain debatable. Using a computerized dynamic activation display, 108 episodes of atrial and ventricular tachycardia and fibrillation in isolated and intact canine cardiac tissues, as well as in vitro swine and myopathic human cardiac tissues, were analyzed for patterns of nonstationary, spiral wave tip motion. Among them, 46 episodes were from normal animal myocardium without pharmacological perturbations, 50 samples were from normal animal myocardium, either treated with drugs or had chemical ablation of the subendocardium, and 12 samples were from diseased human hearts. Among the total episodes, 11 of them had obvious nonstationary spiral tip motion with a life span of 〉2 cycles and with consecutive reentrant paths distinct from each other. Four patterns were observed: (1) meandering with an inward petal flower in 2; (2) meandering with outward petals in 5; (3) irregularly concentric in 3 (core moving about a common center); and (4) drift in 1 (linear core movement). The life span of a single nonstationary spiral wave lasted no more than 7 complete cycles with a mean of 4.6±4.3, and a median of 4.5 cycles in our samples. Conclusion: (1) Patently evident nonstationary spiral waves with long life spans were uncommon in our sample of mostly normal cardiac tissues, thus making a single meandering spiral wave an unlikely major mechanism of fibrillation in normal ventricular myocardium. (2) A tendency toward four patterns of nonstationary spiral tip motion was observed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The RP14 autosomal recessive Retinitis pigmentosa (arRP) locus has been mapped to a 2cM region of chromosome 6p21.3 (refs 1–3). TULP1 (the gene encoding tubby-like protein 1) is a candidate target for the disease mutation because it maps to the RP14 minimum genetic region and because a ...
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 17 (1970), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SYNOPSIS. The life cycles of 2 strains of Allogromia laticollaris (CSH and TPA) raised on experimentally restricted diets have been studied. Cloned cultures of the strains differed in nutritional requirements for continuous reproduction. The TPA strain was more fecund. Both strains have a basically apogamic (asexual) life cycle; only occasionally were gamonts (sexually reproducing individuals) produced. They were autogamous (self-fertilizing) and fusion of the gametes took place within the parental test.We found in CSH clones a regular alternation of vesicularly nucleated and compactly multinucleated diploid generations. The details of the life cycle of either strain are not known well enough to be able to construct life cycle diagrams more meaningful than that of Arnold. The 2 strains studied differ in cytologic and nuclear detail from each other and from the strain studied by Arnold.
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To characterize the signalling molecules produced from the uncleaved Hh precursor U, we determined the site of autoproteolysis and the structures of the cleaved products using a purified Hh protein from a bacterial source. This purified protein, His6C, contains primarily carboxy-terminal sequences ...
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 10 (1972), S. 167-176 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Monhystera denticulata Timm, a free-living nematode present in the aufwuchs assemblages of several marine macrophytes located in North Sea Harbor, Southampton, New York, was isolated from Zostera marina and established in laboratory culture in order to study the influences of temperature and salinity on its life history. Under experimental conditions, M. denticulata has a generation time (Measured as the time elapsing between the first egg depositions of consecutive generations) of 10–12 days at 25° C and 26‰ S, which represent optimal growth conditions in the laboratory. The organism has a generation time of 20 days at 25° C and 13‰, 17 days at 25° C and 39‰, 18 days at 15° C and 26‰, 36 days at 15° C and 13‰ and 34 days at 15° C and 39‰. As conditions vary from the optimum of 25° C and 26‰ S, a decrease in temperature of 10° C and an increase or decrease in salinity of 13‰ results in a doubling of the generation time. At 5° C the generation time is about 180–197 days. Assuming optimum conditions and average generation time, about 15 generations of M. denticulata could occur in North Sea Harbor during the year. The number of generations occurring in reality is probably less, however, due to the fact that the females deposit their eggs over a period of several days.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 12 (1973), S. 303-314 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chromadora macrolaimoides Steiner, a free-living nematode present in the aufwuchs assemblages of several marine macrophytes located in North Sea Harbor, Southampton, New York, was isolated from Enteromorpha intestinalis and established in laboratory culture, where its life history and feeding habits were studied. Under the experimental conditions (25 C and 26‰ S) the worm has an average generation time (22 days) and average life span (45 days) similar to other chromadorids which have been studied in the laboratory. Tracer-feeding experiment with 32P-labelled bacteria, diatoms and chlorophytes indicate selectivity by the worm in both the ingestion and apparent digestion of potential food organisms, with the diatoms and chlorophytes being the preferred foods. Out of a total of 20 species of algae and 14 species of bacteria, two species of diatoms (Nitzschia acicularis and Cylindrotheca closterium) were found which are capable of sustaining indefinite growth. Bacteria-free culture has not been established, however, due to the extreme sensitivity of the worm to antibioties. A comparison of the feeding habits of C. macrolaimoides with Rhabditis marina, another marine nematode fed the same potential food organisms is made, and the influence of selective feeding on the spatial and temporal distribution of marine nematodes is discussed.
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