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1.
John P. Dittami 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(5):641-647
Summary Populations of Reichenow's weavers and rufous sparrows living at the equator were investigated and compared for seasonality in breeding, moulting and fluctuations in the plasma titers of LH, testosterone (in males) and estradiol (in females). These species did not breed during the dry season and they commenced breeding at the onset of the heavy rains (April). In both species, the change from the dry season to the rainy season was accompanied by dramatic increases in gonadal size and steroidogenesis. Surprisingly, plasma titers of the hypophysial hormone LH were not affected.Differences were found in the length of the breeding season: in the weavers it was terminated in September whereas the sparrows bred through January, the end of the study. The differences between the two species in the absence of a pronounced dry season are assumed to be related to the sparrow's ability to interrupt moult and renest in fall when environmental conditions are favourable. in the weavers, no differences in the seasonal changes in gonadal size and plasma titers of LH, T (males) and E2 (females) were found between wet and dry post-heavy rain periods (October–January) whereas differences were found in the sparrows.Abbreviations
E2
estradiol
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T
testosterone
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LH
luteinizing hormone 相似文献
2.
E. Gwinner G. Gänshirt J. Dittami 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1989,165(1):35-39
Summary In the European starling,Sturnus vulgaris, circannual rhythms in gonadal size, molt and other related functions persist only in photoperiods close to 12 h, but are absent in longer or shorter daylengths. To find out whether the arrhythmia seen in long photoperiods results from an arrest of the underlying clock system, three groups of male starlings were held for 10, 14, or 20 months in a 13 h photoperiod and then transferred to a 12 h photoperiod. A control group was held in the 13 h photoperiod throughout the experiment for 28 months. During the initial exposure to the 13 h photoperiod, all birds went through a gonadal cycle, followed by a complete molt. Subsequently, the control birds retained small testes to the end of the experiment and there was no further molt. In contrast, most of the experimental birds re-initiated a testicular cycle, following transfer to the 12 h photoperiod and molted after its completion. The latency between the transfer to the 12 h photoperiod and the onset of testicular growth was not significantly different among the three groups, indicating that the underlying circannual clock had been arrested in the 13 h photoperiod and restarted in the 12 h photoperiod. The pattern of the second testicular cycle did, however, differ among groups. Particularly its amplitude decreased from group 1 to group 3, suggesting that the capacity of the birds to respond to a 12 h photoperiod decreased with increasing duration of exposure to the 13 h photoperiod.Dedicated to Prof. Dr. C.S. Pittendrigh on the occasion of his seventieth birthday. 相似文献
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Didone?FrigerioEmail author Katharina?Hirschenhauser Erich?M?stl John?Dittami Kurt?Kotrschal 《Acta ethologica》2004,7(1):9-18
Testosterone modulates male vertebrates sexual and social behaviour. We experimentally investigated the testosterone-sensitive behaviours in male greylag geese (Anser anser) by implanting silastic tubes containing crystalline testosterone during the mating season (February; 5 implanted and 5 control males) and in the early winter (November; 7 and 7). Focal animals were part of a semi-tame, unrestrained flock with fully intact social relationships. Excreted testosterone and corticosterone immunoreactive metabolites (TM, BM) were determined by enzyme immunoassay. Individual faecal samples and behavioural protocols were collected daily over a period of 5 weeks, including 1 control week before implantation. In February, no significant behavioural effects of the supplemental testosterone were observed, which may be due to the naturally occurring high systemic androgen levels in spring. In November, however, implanted males had higher TM excretion rates and performed status signalling behaviour (beak up) more frequently than control males. No differences between implanted and control males were found with respect to BM, agonistic interactions or vigilance behaviour. Furthermore, during the second week after implantation, TM positively correlated with the frequency of beak up of implanted males, whilst their female partners were attacked with lower latency by other members of the flock than the females of control males. Hence, status signalling in greylag ganders seems to be testosterone-sensitive year-long and inappropriate status signalling of males may draw attacks towards their females. 相似文献
6.
Totzke U Hübinger A Dittami J Bairlein F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):627-631
To investigate the proximate influence of a changing food availability on the seasonal fattening of migratory birds, garden
warblers (Sylvia borin) following postnuptial moult were food restricted once a week. Body mass, food intake, plasma hormone and metabolite levels
were measured and compared to birds which always had ad libitum food access. The food-restricted birds increased their body
mass significantly earlier than the controls. The accelerated fattening was initially not accompanied by hyperphagia and may
be due to either an increased food utilisation efficiency or a reduced metabolic rate. An increase of basal glucagon and corticosterone
and a decrease of insulin levels prior to fattening were not significant, however, they resulted in a significant decrease
of the insulin:glucagon ratio. This ratio was also lower in food-restricted birds than in control birds and may account for
the difference in the fattening progress. We conclude that seasonal fattening may be stimulated by a catabolic impulse which
could be imposed in free-living birds by a decrease of food availability and/or by an increase of energy expenditure. A negative
energy balance is hypothesised to be a common proximate factor affecting migratory as well as winter fattening.
Accepted: 24 August 2000 相似文献
7.
van Dijken JP Bauer J Brambilla L Duboc P Francois JM Gancedo C Giuseppin ML Heijnen JJ Hoare M Lange HC Madden EA Niederberger P Nielsen J Parrou JL Petit T Porro D Reuss M van Riel N Rizzi M Steensma HY Verrips CT Vindeløv J Pronk JT 《Enzyme and microbial technology》2000,26(9-10):706-714
To select a Saccharomyces cerevisiae reference strain amenable to experimental techniques used in (molecular) genetic, physiological and biochemical engineering research, a variety of properties were studied in four diploid, prototrophic laboratory strains. The following parameters were investigated: 1) maximum specific growth rate in shake-flask cultures; 2) biomass yields on glucose during growth on defined media in batch cultures and steady-state chemostat cultures under controlled conditions with respect to pH and dissolved oxygen concentration; 3) the critical specific growth rate above which aerobic fermentation becomes apparent in glucose-limited accelerostat cultures; 4) sporulation and mating efficiency; and 5) transformation efficiency via the lithium-acetate, bicine, and electroporation methods. On the basis of physiological as well as genetic properties, strains from the CEN.PK family were selected as a platform for cell-factory research on the stoichiometry and kinetics of growth and product formation. 相似文献
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Lindström Irene Bontell Neil Hall Kevin E Ashelford JP Dubey Jon P Boyle Johan Lindh Judith E Smith 《Genome biology》2009,10(5):R53-17
Background
Toxoplasma gondii is a zoonotic parasite of global importance. In common with many protozoan parasites it has the capacity for sexual recombination, but current evidence suggests this is rarely employed. The global population structure is dominated by a small number of clonal genotypes, which exhibit biallelic variation and limited intralineage divergence. Little is known of the genotypes present in Africa despite the importance of AIDS-associated toxoplasmosis. 相似文献10.
Luaine Bandounas Nick JP Wierckx Johannes H de Winde Harald J Ruijssenaars 《BMC biotechnology》2011,11(1):1-11