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  • 1
    Electronic Resource
    Electronic Resource
    Voluntary control of human gait: conditioning of magnetically evoked motor responses in a precision stepping task (1999)
    Springer
    Experimental brain research 126 (1999), S. 583-588 
    Details
    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
    URL: http://dx.doi.org/10.1007/s002210050767
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  • 2
    Electronic Resource
    Electronic Resource
    Histological study of the development and sex differentiation of the gonad in the European eel (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 48 (1996), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb01443.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sex differentiation in the European eel: histological analysis of the effects of sex steroids on the gonad (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 47 (1995), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1095-8649.1995.tb01909.x
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of the ethanol-like discriminative stimulus effects of 5-HT receptor agonists as a function of ethanol training dose (1997)
    Springer
    Psychopharmacology 133 (1997), S. 133-141 
    Details
    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
    URL: http://dx.doi.org/10.1007/s002130050383
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