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  • Anguilla australis  (1)
  • Artemisinin  (1)
  • Asymptotic approximations  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Gonad histology and plasma steroid profiles in wild New Zealand freshwater eels (Anguilla dieffenbachii and A. australis) before and at the onset of the natural spawning migration. II. Males (1998)
    Springer
    Fish physiology and biochemistry 19 (1998), S. 339-347 
    Details
    ISSN: 1573-5168
    Keywords: spawning migration ; spermatogenesis ; freshwater eels (Teleostei) ; Anguilla dieffenbachii ; Anguilla australis ; male ; histology ; steroid profiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Immature and maturing male New Zealand freshwater eels, the shortfinned Anguilla australis and the longfinned A. dieffenbachii, were caught from the wild to obtain data on the natural reproductive physiology of these fish. Plasma samples were analysed for steroid hormones by radioimmunoassay and values related to the developmental stage of the testes. Our histological observations on testes largely confirmed those reported previously. Thus, the gonad of non-migrating eels often appeared undifferentiated or poorly developed, containing only type A or early type B spermatogonia. In contrast, the testes of migrating shortfins were in early spermatogenesis as evidenced by the presence of late type B spermatogonia. Similarly, early spermatogenic stages were common in migratory longfins, but eels in midspermatogenesis (all germ cell stages present) were also encountered. Unlike a previous study, patches of testicular regression were commonly seen in migrants of both species. Levels of several androgens, androstenedione (AD), testosterone and 11-ketotestosterone (KT), were elevated in migrants compared to non-migrants. AD was higher in early to midspermatogenic A. dieffenbachii (0.63 ng ml−1) than in A. australis (0.25 ng ml−1) in the spermatogonial proliferation stage, while the inverse was observed for KT (27.78 ng ml−1 and 50.52 ng ml−1, respectively). Levels of 17,20β-dihydroxy-4-pregnen-3-one were nearly undetectable (less than 0.12 ng ml−1) in all animals. Plasma 17-hydroxyprogesterone concentrations in fyke-caught eels were elevated to a greater extent in non-migrants (up to 1.92 ng ml−1) than in migrants (around 0.5 ng ml−1), and correlated well with levels of cortisol in all groups. Histological results are compared to previous studies and the presence of regression in the testes is discussed. In addition, the role of steroid hormones, in particular AD and KT, in reproduction and stress is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007767330225
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Arteether-induced brain injury in Macaca mulatta. I. The precerebellar nuclei: the lateral reticular nuclei, paramedian reticular nuclei, and perihypoglossal nuclei (2000)
    Springer
    Anatomy and embryology 201 (2000), S. 383-397 
    Details
    ISSN: 1432-0568
    Keywords: Key words Lateral reticular nuclei ; Paramedian reticular nuclei ; Perihypoglossal nuclei ; Malaria ; Arteether ; Artemisinin ; Neurotoxicity ; Rhesus monkey ; Antimalarial drugs ; Cerebral malaria ; Macaca mulatta ; Plasmodium falciparum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Malaria poses a threat across several continents: Eurasia (Asia and parts of Eastern Europe), Africa, Central and South America. Bradley (1991) estimates human exposure at 2,073,000,000 with infection rates at 270,000,000, illnesses at 110,000,000, and deaths at 1,000,000. Significant mortality rates are attributed to infection by the parasite Plasmodium falciparum, with an estimated 90% among African children. A worldwide effort is ongoing to chemically and pharmacologically characterize a class of artemisinin compounds that might be promising antimalarial drugs. The U.S. Army is studying the efficacy and toxicity of several artemisinin semi-synthetic compounds: arteether, artemether, artelinic acid, and artesunate. The World Health Organization and the U.S. Army selected arteether for drug development and possible use in the emergency therapy of acute, severe malaria. Male Rhesus monkeys (Macaca mulatta) were administered different daily doses of arteether, or the vehicle alone (sesame oil), for a period of either 14 days, or 7 days. Neuropathological lesions were found in 14-day arteether treated monkeys in the precerebellar nuclei of the medulla oblongata, namely: (1) the lateral reticular nuclei (subnuclei magnocellularis, parvicellularis, and subtrigeminalis), (2) the paramedian reticular nuclei (subnuclei accessorius, dorsalis, and ventralis), and the perihypoglossal nuclei (n. intercalatus of Staderini, n. of Roller, and n. prepositus hypoglossi). The data demonstrate that the simian medullary precerebellar nuclei have a high degree of vulnerability when arteether is given for 14 days at dose levels between 8 mg/kg per day and 24 mg/kg per day. The neurological consequences of this treatment regimen could profoundly impair posture, gait, and autonomic regulation, while eye movement disorders might also be anticipated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050326
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Analytical approximations for iterated bootstrap confidence intervals (1992)
    Springer
    Statistics and computing 2 (1992), S. 161-171 
    Details
    ISSN: 1573-1375
    Keywords: Asymptotic approximations ; bootstrap calibration ; coverage accuracy ; resampling ; saddlepoint methods ; tail probability approximations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Standard algorithms for the construction of iterated bootstrap confidence intervals are computationally very demanding, requiring nested levels of bootstrap resampling. We propose an alternative approach to constructing double bootstrap confidence intervals that involves replacing the inner level of resampling by an analytical approximation. This approximation is based on saddlepoint methods and a tail probability approximation of DiCiccio and Martin (1991). Our technique significantly reduces the computational expense of iterated bootstrap calculations. A formal algorithm for the construction of our approximate iterated bootstrap confidence intervals is presented, and some crucial practical issues arising in its implementation are discussed. Our procedure is illustrated in the case of constructing confidence intervals for ratios of means using both real and simulated data. We repeat an experiment of Schenker (1985) involving the construction of bootstrap confidence intervals for a variance and demonstrate that our technique makes feasible the construction of accurate bootstrap confidence intervals in that context. Finally, we investigate the use of our technique in a more complex setting, that of constructing confidence intervals for a correlation coefficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01891208
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    Paper (German National Licenses)
    Fulltext
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