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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Psychopharmacology 97 (1989), S. 45-50 
    ISSN: 1432-2072
    Keywords: DRL ; Ethanol ; Operant behavior ; Rats ; Residual tolerance ; Tolerance ; Rate increases and decreases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Six male Sprague-Dawley rats were trained on a DRL-20 operant schedule for food presentation. When stable performance was established, they were exposed to an escalating regimen of daily ethanol administration (1.125–3.75 g/kg. IP). This dosing regimen continued until the maximally tolerable dose for each subject was reached. Tolerance loss then was monitored for approximately 6 months by periodic ethanol challenge doses (1.5 g/kg). Dose-effect curves (DECs) were obtained prior to (DEC-1), immediately after (DEC-2), and 6 months following termination of (DEC-3) the ethanol exposure. Rate-increasing effects (DEC-1) were noted at low doses (0.75 and 1.125 g/kg), with a higher dose (2.25 g/kg) resulting in a decreased rate of responding. Tolerance, following chronic ethanol exposure, developed to both the rate-increasing and ratedecreasing effects of ethanol (DEC-2). While some tolerance was lost within the 6 months following the daily ethanol exposure (DEC-3), a significant degree of tolerance was still indicated by most of the response measures. This duration of tolerance was considerably longer than that generally reported, and is probably attributable to persistent learned compensatory behavior and/or intermittent ethanol challenge tests.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2072
    Keywords: Behavioral tolerance ; Ethanol ; Operant behavior ; Rats ; Residual tolerance ; Tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Twelve male Sprague-Dawley rats, following training on one of two food-motivated operant schedules (Fixed-Ratio 30 or Variable Interval 30 s), were exposed to an escalating regimen of daily ethanol (1.125–3.0 g/kg, IP) administration. This increasing dose regimen continued until the maximally tolerable dose for each subject was reached. Tolerance was then monitored for approximately 6 months by periodic ethanol challenge doses (1.5 g/kg). Dose-effect curves (DECs) were obtained prior to chronic ethanol (DEC1), immediately after ethanol tolerance development (DEC2), and 6 months (DEC3) following termination of ethanol exposure. At DEC1, ethanol produced dose-dependent decreases in rate on both schedules with no significant schedule differences in ED50 (the dose effective at reducing the maximal response rate by one-half) values. Maximal tolerance was achieved in means of 46 and 55 days on the VI and FR schedules, respectively. Differences in rate of tolerance acquisition on the initial dose of the chronic regimen (1.125 g/kg) account for most of the difference in the overall rate of acquisition. Comparison of the ED50 data from DECs 1 and 2 indicated that daily ethanol exposure resulted in a 2-fold decrease in ethanol sensitivity (i.e., tolerance) on both operant schedules. The ED50 data from DECs 1 and 3 demonstrated a 1.7-fold decrease in ethanol potency on DEC3. This duration of tolerance was considerably longer than that generally reported, and possibly related to the extended ethanol exposure and the sensitivity of operant schedules to drug effects.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2072
    Keywords: Ethanol ; Operant performance ; Tolerance ; Intoxicated practice ; Compensatory behaviors ; Acute ethanol withdrawal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acquisition and retention of tolerance to ethanol's rate-decreasing effects on operant performance were examined in rats which received a 52-day regimen of ethanol or saline injections prior to and/or after each daily session. Eight groups of rats differed on: (a) number of days with intoxicated practice (pre-session ethanol); (b) intermittent (spaced) or daily (massed) intoxicated practice; and (c) post-session ethanol or saline on nonintoxicated practice days. Massed practice groups were given their presession saline days prior to their pre-session ethanol days. Ethanol dose-effect tests were given prior to, during, and after the chronic injection regimen. Under both spaced and massed practice conditions, the magnitude of tolerance developed increased directly with the number of pre-session ethanol days, even when absolute ethanol exposure was constant. No group showed complete tolerance loss. The post-session ethanol supplements (a) facilitated tolerance development in spaced practice groups and tolerance loss in massed practice groups, (b) blocked ethanol's low dose rate-increasing effects, and (c) produced an acute withdrawal-like performance disruption the next day. The results suggest that both intoxicated practice and practice during acute ethanol withdrawal influence the acquisition and retention of compensatory behaviors during ethanol tolerance development.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: Methadone ; Cyclic AMP ; Tolerance ; Physical dependence ; Withdrawal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Laboratory and animal investigations have supported the hypothesis that levels of cyclic AMP are stable during tolerance to narcotic drugs and increased during withdrawal. In order to test this hypothesis, serial 24-h urinary excretion of cyclic AMP by long-term methadone addicts was determined during a period of stable methadone intake, a period of gradual withdrawal, and a period of acute withdrawal. Cyclic AMP excretion during stable methadone intake is identical to that of normal control subjects. Neither gradual nor acute withdrawal appears to affect the urinary excretion of cyclic AMP. These data agree with previous reports in the literature which suggest that cyclic AMP levels are not altered during tolerance to narcotics, but do not support the hypothesis that levels of the nucleotide might be increased during withdrawal.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2072
    Keywords: Ethanol ; Tolerance ; Operant performance ; Delayed ethanol effect ; Drug-induced compensatory learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of pre-session and post-session daily ethanol injections on the development and loss of tolerance to ethanol's effects on fixed ratio operant performance in rats was assessed using a cumulative dosing procedure. Daily pre-session ethanol administration produced a greater decrease in ethanol sensitivity than did daily post-session ethanol. Both tolerance effects persisted for at least 1 month after the chronic injection phase. No changes in ethanol sensitivity were apparent in the saline control group and no changes in estimated blood ethanol levels were found after the chronic treatments. The post-session ethanol groups displayed a performance decrement during the initial segment of the chronic injection period, but improved significantly across the chronic phase. These data suggest that some delayed effect of ethanol initially impaired performance but that tolerance to this ethanol effect also occurred and probably contributed to the decline in ethanol sensitivity seen in these groups. Compensatory learning as the mechanism for tolerance development in the pre-session and post-session ethanol groups was supported by the finding of no change in ethanol sensitivity in rats exposed to comparable daily ethanol without any concurrent operant task on which the direct, immediate, or indirect, delayed ethanol effects could operate.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 10 (1984), S. 161-170 
    ISSN: 1573-1561
    Keywords: Ferulic acid ; allelopathy ; temperature stress ; sorghum ; soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Experiments were conducted to test the hypothesis that alleiopathic effects of ferulic acid (FA) may be altered by the temperature conditions of the growth environment. Growth of grain sorghum and soybean seedlings over a 10-day treatment period showed that a significant interaction effect occurred between environmental temperatures and FA treatments. Sorghum grown with an average day temperature of 37 °C and soybeans grown at 34 °C had greater dry weight reductions caused by FA than when the respective environments were 8 °C and 11 °C lower. The threshold concentration for inhibition of sorghum growth was 0.2 mM FA under the hot conditions and 0.4 mM FA with the cooler conditions. Soybeans were more sensitive than sorghum, and these inhibition thresholds for the hot and cool environments were 0.1 and 0.25 mM FA. These results demonstrate that temperature stress enhances allelochemical inhibition and indicate that interactions with the environment are an important consideration for understanding allelopathy.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 14 (1988), S. 1829-1844 
    ISSN: 1573-1561
    Keywords: Allelochemicals ; allelopathy ; autotoxicity ; bioregulators ; crop production ; crop residue ; herbicides ; no-tillage ; phytotoxins ; weed control ; weed interference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Strategies for utilizing allelopathy as an aid in crop production include both avoidance and application protocols. There are immediate opportunities for management of weed and crop residues, tillage practices, and crop sequences to minimize crop losses from allelopathy and also to use allelopathic crops for weed control. Varieties of grain and forage sorghums (Sorghum Spp.), sunflower (Helianthus annuus L.), oats (Avena sativa L.), wheat (Triticum sativum L.),rye (Secale cereale L.), and others may provide weed control and in some instances crop stimulation from their residues. Our four-year field study with cultivated sunflower resulted in no differences in weed biomass between plots with and without herbicide (EPTC) applications. Strip cropping that included sorghum showed that in the subsequent year weed density and biomass were significantly lower in the previous-year sorghum than in soybean strips. Possibilities exist for modification of crop plant metabolism to alter production of allelochemicals. Allelochemical-environmental interactions must be considered in efforts to benefit from allelopathy. Under greenhouse conditions, joint application of low levels of atrazine, trifluralin, alachlor, or cinmethylin with a phenolic allelochemical showed that these two categories of inhibitors acted in concert to reduce plant growth. Allelochemicals may also be adapted as yield stimulants or environmentally sound herbicides, such as cinmethylin and methoxyphenone. Isolation of bialophos, tentoxin, and others shows that bacteria and fungi are good sources of biologically active compounds.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 18 (1992), S. 197-207 
    ISSN: 1573-1561
    Keywords: Sorgoleone ; mitochondria ; inhibitor ; allelochemical ; allelopathy ; root exudate ; Sorghum bicolor ; electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aim of this investigation was to determine if sorgoleone (SGL), a hydrophobic compound inSorghum bicolor (L.) Moench root exudate, interferes with mitochondrial functions. Tests were conducted on mitochondria isolated from etiolated soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seedlings. The data show SGL is a potent inhibitor of state 3 and state 4 respiration rates in both soybean and corn. Using either NADH, succinate, or malate as substrate, the I50 was about 0.5μM SGL for state 3 and 5.0μM for state 4 based on 0.3–0.5 mg mitochondrial protein. Absorption spectra indicate SGL blocks electron transport at theb-c 1 complex. These data show that disruption of mitochondrial function may be a mechanism of SGL-mediated growth inhibition previously reported and demonstrate a probable role of SGL inSorghum allelopathy.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 25 (1999), S. 1611-1621 
    ISSN: 1573-1561
    Keywords: Hydroquinone ; allelopathy ; plant water balance ; photosynthesis ; chlorophyll fluorescence ; 13C isotopes ; leafy spurge ; Euphorbia esula ; small everlasting ; Antennaria microphylla Rydb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Field observations indicate leafy spurge (Euphorbia esula) is inhibited by the presence of Antennaria microphylla. Hydroquinone (HQ), one of several compounds isolated from A. microphylla has been shown to inhibit leafy spurge seed germination, root elongation, and callus culture growth. The present study was designed to analyze the effects of HQ on water relations and photosynthesis of leafy spurge. Plants grown in 0.25 mM HQ had consistently higher leaf diffusive resistance and lower transpiration rates than control plants (P 〈 0.05). Chlorophyll fluorescence was significantly lower than controls (P 〈 0.05) towards the end of the treatment period. At the end of the treatment, tissue from 0.25 mM HQ plants had higher levels of 13C, indicating there had been a sustained interference with stomatal function. These data suggest that a disruption of the plant water balance is one mechanism of leafy spurge inhibition by A. microphylla.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-1561
    Keywords: Caffeic acid ; allelopathy ; plant water balance ; photosynthesis ; chlorophyll fluorescence ; 13C carbon isotopes ; leafy spurge ; Euphorbia esula ; small everlasting ; Antennaria microphylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Leafy spurge (Euphorbia esula), a native perennial weed introduced from Eurasia around the turn of the century, disrupts natural and agroecosystems across much of the Northern Great Plains. While leafy spurge displaces many native plant species, it has been demonstrated that small everlasting (Antennaria microphylla), a native perennial, is allelopathic to leafy spurge. Caffeic acid (CA), one of three compounds isolated from small everlasting, inhibits leafy spurge seed germination, root elongation, and callus culture growth. This study investigated the mechanism of this interference at the whole-plant level. Results indicate that inhibition of growth in leafy spurge after exposure to CA is primarily due to a disruption of plant–water relations. Leafy spurge cuttings were propagated in 0.5 strength Hoagland's nutrient solution for 30 days. For treatments, six plants were transferred into nutrient medium amended with either 0.1 or 0.25 mM CA for a period of 30 days. To determine the effect of pH, two additional groups of six plants were grown in nutrient medium adjusted with HCl corresponding to pH levels of plants treated with CA (pH 5.5–5.8 for 0.1 mM CA and pH 4.5–4.8 for 0.25 mM CA). By day 12 of the treatment period, plants treated with both levels of CA had significantly higher leaf diffusive resistances than control plants. Plants grown at the corresponding pH levels experienced higher diffusive resistances later in the treatment period (day 21). Transpiration was similarly affected with treated plants showing relatively higher transpiration rates compared to controls. Chlorophyll fluorescence was significantly lower than controls in all treated plants by end of the treatment period. The stable carbon isotope ratio (13C:12C) in these plants was higher than controls. These data show that a disruption of plant water relations is the primary mechanism of plant growth inhibition.
    Type of Medium: Electronic Resource
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