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  • Electronic Resource  (8)
  • 1995-1999  (4)
  • 1985-1989  (2)
  • 1975-1979  (2)
  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Industrial and engineering chemistry 25 (1986), S. 878-885 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 48 (1996), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The histological structure of the gonads was studied in yellow eels sampled from a coastal lagoon and from stocks reared in an aquaculture plant showing different sex ratios. Gonad development related to body size rather than to age and underwent an intermediate stage characterized by a structure of an early testis but containing oogonia and oocytes. This gonad was called the Syrski organ and the stage juvenile ambisexual. Ovaries were found in eels from 22–30 cm in length, possibly derived from undifferentiated gonads or from Syrski organs. Fully differentiated testes were found in eels 〉35 cm, derived from Syrski organs. These observations support the results of previous research. From elvers and in eels up to 15–16 cm in length, growth of the gonadal primordium is due to primordial germ cell migration. In eels 〉 15 cm multiplication of primordial cells begins. Oogonial clones were found in eels 〉 18 cm in length, whilespermatogonium B clones were observed in eels 〉30 cm in length. The dynamics of sex differentiation was different among stocks with different ultimate sex ratios: ovaries were found in shorter eels in stocks with a prevalence of females, in longer eels in stocks with a prevalence of males. This result supports the hypothesis of a metagametic (environmental) sex determination. The somatic cells in contact with germ cells and those in the interstitium appeared early during gonad development and preceded germ cell differentiation. This suggests that somatic cells are the targets of the environmental factors influencing sex differentiation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 47 (1995), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of sex steroids on sex differentiation in the European eel were studied. The steroids, 17α-methyltestosterone (MT) and 17α-ethynylestradiol (EE), were given in the diet to 6–8 cm elvers and to 15–18 cm and 22–25 cm yellow eels. In our rearing conditions a very large percentage of the untreated eels developed as males. No masculinizing effect of MT could be demonstrated. The EE, administered at a dose of 10 mg kg-1 of diet to 6–8 cm elvers and 15–18 cm eels, induced ovarian differentiation in about 90 and 65% of eels respectively, while in the control 〈5% of females was recorded. In 22–25 cm yellow eels a moderated feminizing effect was observed.Histological analysis of the gonads of treated eels showed that sex steroids affect the gonadal structure. The androgen stimulates hypertrophy of compact connective tissue, early differentiation of Leydig cells, Sertoli cells and early formation of the spermatic duct. Oestrogen inhibits the differentiation of these structural components and stimulates the differentiation of follicular cells and an ovarian structure.The involvement of gonadal structural components is discussed in relation to the effect of steroid treatment and to the peculiarities of sex differentiation in the European eel.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 264 (1976), S. 344-345 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The asymmetry would arise in a ring of synchronously rotating, irregularly shaped, particles if there was a statistical tendency for the long axes of the particles to be inclined in the trailing sense with respect to the differential rotation. Such an orientation of the axes of the particles could ...
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1572-9648
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Summary A Shuttle-borne tethered satellite has the potential of contributing significantly to the scientific versatility of the Shuttle Orbiter, that will be launched by NASA in the early '80s. If the Shuttle is in a 200 km orbit, the use of a 100 km tether connected to the Shuttle at one end and to the satellite at the other makes the performance of various relevant electromagnetic measurements in the magnetosphere possible. The tethered satellite (a subsatellite) can also be lowered from the Shuttle down to heights in the vicinity of 100 km, to an altitude band that has great importance from the standpoint of both upper atmospheric experimentation and gravity-gradient measurements. From a preliminary analysis, we find that one of the major problem areas of the system — the heating of the wire and of the subsatellite due to air drag — can be solved within the present state of the art in wire technology and heat shielding. System masses are also reasonable: In fact, a system with a 100 km wire and a Shuttle-borne reel, tethering a 100 kg subsatellite, would have a mass no larger than 120 kg.
    Notes: Sommario Satelliti collegati con cavo allo Shuttle in orbita contribuiscono in modo significativo alla versatilità del veicolo. Se lo Shuttle è in orbita a 200 km di altezza, l'uso di un cavetto lungo 100 km attaccato con un estremo allo Shuttle e con l'altro ad un satellite rende possibile una grande varietà di misure elettromagnetiche nella magnetosfera. Il satellite collegato con cavo (un sottosatellite) può essere calato dallo Shuttle giù fino ad altezze dell'ordine di 100 km in una banda di quote che ha una enorme importanza dal punto di vista della sperimentazione dell'alta atmosfera ed inoltre dal punto di vista della misura del gradiente di gravità. Dall'analisi preliminare abbiamo trovato che uno dei maggiori problemi che presenta il sistema, il riscaldamento del filo e del satellite dovuto alla resistenza dell'aria, può essere risolto nell'ambito del presente stato dell'arte nella tecnologia dei cavi e dell'isolamento termico. Le masse del sistema sono anche ragionevoli; infatti un sistema con un cavo lungo 100 km ed un rocchetto sullo Shuttle, collegante un sottosatellite di 100 kg, verrebbe ad avere una massa di 120 kg.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Key words Human gait ; Transcranial magnetic stimulation ; Motor cortex ; Leg flexor/extensor muscle ; Corticospinal input ; Visual control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The aim of this study was to investigate visuomotor control during human gait. It was assumed that visual input should modulate transcranially evoked motor potentials (EMPs) during walking. The effect of transcranial magnetic stimulation (TMS) in a visually guided precision stepping task was compared with that during normal gait. EMPs were studied in tibialis anterior (TA), gastrocnemius (GM), and abductor digiti minimi (AD) muscles during treadmill walking. In both stepping tasks, a facilitation of EMPs was observed prior to activation of the respective leg muscle. EMP facilitation proved to be modulated throughout the stride cycle when normalising EMP with respect to the underlying electromyogram (EMG). Facilitation was strongest in TA prior to the swing phase. Significant differences of EMP facilitation between the visual and control tasks were present. In the visual task, maximal facilitation of TA EMPs prior to and during the swing phase was decreased compared to the control task. Conversely, there was increased facilitation of GM EMPs during swing phase of the visual task, prior to the heel strike and prior to the plantarflexion, which was the moment when the target was hit. Thus, the effect of visual input upon EMPs in TA and GM was differential and reciprocal according to the respective functional state. The results support the hypothesis of a conditioning effect of visual or, alternatively volitional, drive on EMPs during stepping.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2072
    Keywords: Key words Ethanol ; 5-HT ; Rats ; Drug discrimination ; Alcohol ; TFMPP ; mCPP ; RU 24969 ; CGS 12066B ; 8-OH DPAT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  A drug discrimination procedure was used to characterize the ethanol-like effects of a variety of 5-HT1 agonists. Previous studies found that the degree of substitution of the 5-HT1B/2C agonist TFMPP (m-trifluoromethylphenylpiperazine) depended on the training dose of ethanol. The present studies extend this initial finding to four additional 5-HT agonists with different selectivity for 5-HT1A, 5-HT1B, or 5-HT2C receptors: CGS 12066B (7-trifluoromethyl-4(4-methyl-1-piperazinyl)-pyrrolo[1,2-a]quinoxaline maleate), mCPP [1-(3-chlorophenyl)piperazine diHCl], RU 24969 [5-methoxy-3(1,2,3,4-tetrahydro-4-pyridinyl]-1H-indole succinate and 8-OH DPAT [(±)-8-hydroxy-2-(di-n-propylamino)tetralin HBr]. Separate groups of rats were trained to discriminate 1.0 g/kg (n=7), 1.5 g/kg (n=6) or 2.0 g/kg (n=8) ethanol from water. Following training, three to five doses of each 5-HT agonist were tested twice in each rat. The most selective 5-HT1B agonist tested, CGS 12066B (3–17 mg/kg; IP), completely substituted for the 1.0 g/kg ethanol, but not for 1.5 or 2.0 g/kg ethanol. Likewise, the 5-HT1B/2C agonist mCPP (0.56–1.7 mg/kg; IP) completely substituted only in the 1.0 g/kg ethanol training group. The 5-HT1A/1B agonist RU 24969 (0.1–3.0 mg/kg; IP) substituted for all training doses of ethanol, although in a lower proportion of the rats tested in the 2.0 g/kg ethanol training group. Finally, the 5-HT1A agonist 8-OH DPAT (0.1–1.0 mg/kg; IP) did not substitute completely for any ethanol training dose. The results consistently show that agonists with 5-HT1B activity produce discriminative stimulus effects similar to low and intermediate, but not high, ethanol training doses.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Neurological sciences 9 (1988), S. 551-557 
    ISSN: 1590-3478
    Keywords: Depression and neuroticism ; multiple sclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Gli AA hanno eaminato 88 soggetti (36 maschi e 52 femmine) affetti da sclerosi multipla ai quali sono stati applicati i questionari del CES-D e SRT per la valutazione delle reazioni depressive e del nevroticismo. Dalla comparazione dei risultati con quelli del gruppo di controllo, emergono differenze statisticamente significative nella popolazione esaminata per quanto riguarda depressione e somatizzazione mentre i punteggi per ansia ed inadeguatezza risultano normali.
    Notes: Abstract 88 subjects (36 males and 52 females) affected by multiple sclerosis (MS), were studied with the CES-D and SRT tests for the evaluation of depressive reactions and neuroticism. Comparing the results with those of the control group, we found a significant score for depression and somatization in the MS patients, whereas the scores for anxiety and inadequacy were normal.
    Type of Medium: Electronic Resource
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