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Setiawan AN Davis LS Darby JT Lokman PM Young G Blackberry MA Cannell BL Martin GB 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2006,145(3):357-362
Penguins show varying degrees of brood reduction behavior, from obligate brood reducers to brood maximizers, and we hypothesize that this is associated with differences in prolactin secretion. To address this hypothesis, we determined the breeding season prolactin profile of the yellow-eyed penguin (Megadyptes antipodes) for comparison with those of other penguin species found in the literature. We also measured sex steroid plasma concentrations to better characterize the reproductive cycle of the species. Plasma concentrations of prolactin increased from early in the season, reaching a peak during late incubation, and remained elevated up to the guard period. This general pattern was similar to that of other penguins for which we have corresponding data. However, we found that throughout the laying period, prolactin titers in yellow-eyed penguins remained elevated while they fell to basal levels after the laying of the first egg in macaroni penguins, which corresponds to differences in incubation behavior during this time. We conclude, therefore, that differences in the brood reduction behavior in penguins, may be reflected in the pattern of PRL concentrations around the time of egg laying. 相似文献
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Most estrous cycles in cows consist of 2 or 3 waves of follicular activity. Waves of ovarian follicular development comprise
the growth of dominant follicles some of which become ovulatory and the others are anovulatory. Ovarian follicular activity
in cows during estrous cycle was studied with a special reference to follicular waves and the circulating concentrations of
estradiol and progesterone. Transrectal ultrasound examination was carried out during 14 interovulatory intervals in 7 cows.
Ovarian follicular activity was recorded together with assessment of serum estradiol and progesterone concentrations. Three-wave
versus two-wave interovulatory intervals was observed in 71.4% of cows. The 3-wave interovulatory intervals differed from
2-wave intervals in: 1) earlier emergence of the dominant follicles, 2) longer in length, and 3) shorter interval from emergence
to ovulation. There was a progressive increase in follicular size and estradiol production during growth phase of each wave.
A drop in estradiol concentration was observed during the static phase of dominant anovulatory follicles. The size of the
ovulatory follicle was always greater and produced higher estradiol compared with the anovulatory follicle. In conclusion,
there was a predominance of 3-wave follicular activity that was associated with an increase in length of interovulatory intervals.
A dominant anovulatory follicle during its static phase may initiate the emergence of a subsequent wave. Follicular size and
estradiol concentration may have an important role in controlling follicular development and in determining whether an estrous
cycle will have 2 or 3-waves. 相似文献
36.
The O-antigen chain from the lipopolysaccharide of Helicobacter pylori
strain UA861 was determined to be composed of an elongated type 2 N -
acetyllactosamine backbone,
-[-->3)-beta-D-Gal-(1-->4)-beta-D-GlcNAc-(1- ]n-->, with
approximately half of the GlcNAc units carrying a terminal alpha-d-Glc
residue at the O -6 position. The O-chain of H.pylori UA861 was terminated
by a N -acetyllactosamine [beta-D-Gal-(1-->4)-beta-D- GlcNAc] (LacNAc)
epitope and did not express terminal Lewis X or Lewis Y blood-group
determinants as previously found in other H.pylori strains. The absence of
terminal Lewis X and Lewis Y blood-group epitopes and the replacement of
Fuc by Glc as a side chain in the O- chain of H.pylori UA861 represents yet
another type of lipopolysaccharide structure from H.pylori species. These
structural differences in H.pylori lipopolysaccharide molecules carry
implications with regard to possible different pathogenic events between
strains and respective hosts.
相似文献
37.
Spatial non-uniformities in [Ca2+]i during excitation-contraction coupling in cardiac myocytes. 总被引:15,自引:8,他引:7
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The intracellular calcium ([Ca2+]i) transient in adult rat heart cells was examined using the fluorescent calcium indicator fluo-3 and a laser scanning confocal microscope. We find that the electrically evoked [Ca2+]i transient does not rise at a uniform rate at all points within the cell during the [Ca2+]i transient. These spatial non-uniformities in [Ca2+]i are observed immediately upon depolarization and largely disappear by the time the peak of the [Ca2+]i transient occurs. Importantly, some of the spatial non-uniformity in [Ca2+]i varies randomly in location from beat to beat. Analysis of the spatial character of the non-uniformities suggests that they arise from the stochastic nature of the activation of SR calcium-release channels. The non-uniformities in [Ca2+]i are markedly enhanced by low concentrations of Cd2+, suggesting that activation of L-type calcium channels is the primary source of activator calcium for the calcium transient. In addition, the pattern of calcium release in these conditions was very similar to the spontaneous calcium sparks that are observed under resting conditions and which are due to spontaneous calcium release from the SR. The spatial non-uniformity in the evoked [Ca2+]i transient under normal conditions can be explained by the temporal and spatial summation of a large number of calcium sparks whose activation is a stochastic process. The results are discussed with respect to a stochastic local control model for excitation-contraction (E-C) coupling, and it is proposed that the fundamental unit of E-C coupling consists of one dihydropyridine receptor activating a small group of ryanodine receptors (possibly four) in a square packing model. 相似文献
38.
The first Australian record of the lily thrips, Liothrips vaneeckei Priesner, is reported from a bulb farm in Warragul South, Victoria. It is an occasional pest of Lilium bulbs, both in the field and in storage, particularly in the USA and several European countries, and is also infrequently found in considerable numbers on the corms of orchids. 相似文献
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