Effect of Darkness on Growth and Flowering of Chenopodium rubrum and C. murale Plants in vitro

Chenopodium rubrum, a short-day plant, and C. murale, a long-day plant, were grown in vitro in continuous darkness. Control C. rubrum plants exposed to continuous darkness for 15 d at cotyledonary phase, did not flower, while 80 % of plants flowered on the medium with 5 % glucose and 10 mg dm⁻³ GA₃. Control C. murale plants exposed to continuous darkness for 10 d at the age of 4^th pair of leaves, did not flower, while GA₃ (1 – 5 mg dm⁻³) stimulated flowering up to 65 %. This revised version was published online in July 2006 with corrections to the Cover Date.     

Differences in exercise capacity and physiological responses in Wistar rats among breeders

In animal experiments aimed at extrapolation to humans, it is essential to ensure the reproducibility of experiments and universality between animals and humans. However, among animals with the same generic name but from different breeders, which is to say different stocks, even resting physiological conditions, such as genetics, do not coincide, and, therefore, exercise capacity and physiological responses may also vary. To address this issue, we examined the differences in exercise capacity and exercise-induced metabolic and endocrine responses among stocks of Wistar rats using an established treadmill running model for rodents, which mimics physiological responses in humans. Wistar rats from four breeders were acclimated to treadmill running and then had a catheter inserted into their external jugular veins. Subsequently, the rats were subjected to an incremental treadmill running test (IRT). We found that there were significant differences in the exercise capacity among Wistar rats from different breeders. Additionally, the dynamics of blood lactate, glucose, and adrenocorticotropic hormone levels during the IRT were found to vary among the Wistar rats from different breeders; only one stock showed human-type exercise-induced physiological responses. These results indicate that Wistar rats could have different capacities for and physiological responses to the same exercise depending on their stocks. Thus, the selection of the stock of experimental animals may affect the validity of the results when verifying exercise effects.     

Characteristics of embryos from repeat breeder and virgin heifers

The characteristics of 7-day-old embryos non-surgically collected from 35 repeat breeder heifers (RBH) and 24 virgin heifers (VH) were compared by repeated observations within each animal. A higher incidence of the embryos collected from the VH was classified as normal and had reached a more advanced developmental stage than embryos from the RBH. Nearly all VH yielded normal (N) embryos, but morphologically deviated (MD) or degenerated embryos (D) appeared occasionally in many VH. The RBH group contained three subgroups of animals. One group of RBH yielded a high percent of N embryos. A second group yielded mostly MD or D embryos with an occasional N embryo, and the third group only D embryos or no embryos. Heifers from which no embryos were recovered on day 7 yielded uncleaved ova, apparently retarded embryos or no embryos when slaughtered three days after insemination. It is concluded that retarded embryonic development may be a common factor for most RBH. The embryo morphology and the degree of retardation differ among animals and between oestrous periods in the same animal.     

Effect of ormeloxifene on ovariectomy-induced bone resorption, osteoclast differentiation and apoptosis and TGF beta-3 expression

Effect of ormeloxifene, a multifunctional selective estrogen receptor modulator, on prevention of ovariectomy-induced bone resorption in retired breeder female rats, osteoclastogenesis using bone marrow cells from adult Balb/c mice cultured in presence of M-CSF and RANKL, osteoclast apoptosis using terminal deoxynucleotidyl transferase fragment end labeling and TGF beta-3 expression were investigated. Raloxifene, a benzothiophene reported to mimic effects of estrogen in bone, and estradiol were used for comparison. Ormeloxifene (10⁻⁶ and 10⁻⁸ M) significantly inhibited osteoclastogenesis (P < 0.001 versus vehicle control) as evidenced by lower number of TRAP-positive osteoclasts in bone marrow cultures and caused apoptosis of osteoclasts. The effect was almost equivalent to that observed in presence of estradiol-17 beta, except that significant number of cells undergoing apoptosis was evident even at 10⁻⁹ M concentration of estradiol-17 beta (P < 0.001). Raloxifene, though inhibited osteoclastogenesis at much lower concentrations (10⁻⁸ to 10⁻¹² M; P < 0.001), failed to cause apoptosis of osteoclasts at any of the concentrations used. While ormeloxifene, raloxifene and ethynylestradiol significantly prevented ovariectomy-induced bone loss in vivo in retired breeder female rats, prevention of ovariectomy-induced decrease in BMD and trabecular network of proximal tibia, calcium and phosphorus levels in femur and tibia and prevention of ovariectomy-induced down-regulation of TGF beta-3 expression in lumbar vertebrae was of lower order in raloxifene- than ormeloxifene- or ethynylestradiol-supplemented females. Both the SERMs, however, produced considerable estrogenic effects at the uterine level as evidenced by increase in weight, total and endometrial area and luminal epithelial cell height; the effect being generally greater in raloxifene- than ormeloxifene-treated rats. Findings demonstrate that inhibition of estrogen-deficiency osteoporosis by ormeloxifene, as in case of estradiol, was mediated via inhibition of osteoclastogenesis, apoptosis of osteoclasts and up-regulation of TGF beta-3 expression. Raloxifene, though effective in inhibiting osteoclastogenesis in vitro at much lower concentrations, was not only less potent in preventing ovariectomy-induced bone loss in retired breeder female rats in vivo but also appeared to have a different mechanism of action than ormeloxifene and estradiol.     

Transition from absolute to quantitative short-day control in Nicotiana tabacum cv. Maryland Mammoth

The response in vitro of thin cell layers, excised from different stem regions of Nicotiana tabacum cv. Maryland Mammoth plants at various developmental stages, was studied under different photoperiodic treatments. The aim was to determine at which stage of plant development, and in which region of the stem, the absolute short-day requirement, indispensable for the induction of the flowering process in this genotype, becomes quantitative and whether it remains short-day. The explants were cultured on a medium suitable for flower neoformation, and were exposed for 30 days to the following treatments: continuous darkness, 8 h light/16 h dark per day, 16 h light/8 h dark per day, and continuous light. The first flowers on explants were observed from plants that were still in the vegetative state, but whose apex showed an accelerated production of axillary vegetative buds, as observed histologically. These explants were excised from the first 10 internodes below the first node with a leaf ≥ 5 cm in length (apical site), and produced flowers only under short-day treatment. When the apical dome initiated the organization of the terminal flower, the apical site explants developed flowers under both short-day and long-day treatments. At the same stage, explants from the 15th to the 20th internode below the first leaf ≥ 5 cm in length also formed flowers, but only under short-day. When the plant showed a complete inflorescence, flowers were also present on explants from the most basal stem internodes and from the inflorescence branches. At this stage, flower neoformation occurred under all treatments; however, under short-day the number of explants showing flowers not associated with vegetative buds on the same sample greatly exceeded that observed under other treatments, as did the mean number of flowers per explant (except the basal regions). In conclusion, in the post-inductive phases of the flowering process, the photoperiodic requirement of this genotype is always short-day. The superficial tissues of the stem require either absolute or quantitative short-day treatment, depending on their position on the stem and the stage of evolution of the flowering process in the terminal apex.     

Phytochrome and photoperiodic induction

The photoreceptor phytochrome has been extensively characterized at the chromophore, protein and gene level. It consists of a family of red/far-red reversible molecules and the genes for three members have been sequenced. Phytochromes are chromoproteins, which probably exist as dimers in vivo. Photoperiodism in higher plants involves the interaction of phytochrome with an endogenous timekeeping system. The interaction is complex, and several distinct actions of light can be distinguished. The possible involvement of different phytochromes in different actions of light in both long-day plants and short-day plants is discussed. Potential roles for different members of the phytochrome family and homo-and hetero-dimers of phytochrome are proposed.     

Morphometric studies on mink testicular tissue

The mink, a seasonal breeder of great economic importance, shows a high incidence of male infertility. This problem has forced investigators to find methods of assaying male mink infertility. In this study, morphometric studies have been performed on testicular tissue of a total of 31 males eliminated from breeding after testicular palpation, sperm test, and estimation of serum testosterone concentrations. Males having low sperm quality or disturbed testicular development (n=24) had significantly (p<0.01) lower numbers of spermatocytes, spermatids, and freefloating luminal spermatozoa. compared with males with good sperm quality (n=7). No differences were found in the numbers of spermatogonia, Sertoli, and Leydig cells. Other morphometric parameters such as mean diameter, mean area, mean volume, percentage of area, and surface area per volume of nuclei are also presented for each cell type in the testis. It may be concluded that the sperm test is best suited for assessing fertility in mink. Severe disturbances in testicular development can be detected by testicular palpation and serum testosterone measurements.     

Brutph?nologie und Morphometrie des Schwarzbauchmeerl?ufers (Fregetta tropica) auf King George Island, Antarktis

Zusammenfassung Im Jahre 1995/96 wurden brutphänologische und biometrische Daten des Schwarzbauchmeerläuferes (Fregetta tropica) auf King George Island, Antarktis, erhoben.Die Vorbrutzeit erstreckte sich bis Ende Dezember, dem Beginn der Hauptlegephase. Während der Inkubationszeit (Gesamtdauer 39–42 Tage) verweilten die Weibchen im Mittel 1,6 Tage (Männchen 1,8 Tage) auf dem Gelege. Die Häufigkeit von Brutunterbrechungen (Dauer 1,9 Tage) nahm im Laufe der Inkubationszeit drastisch ab. Hauptschlupfzeit der Küken war Anfang bis Mitte Februar. Das Kükenwachstum zeichnete sich durch individuell differenzierte Massezunahme aus. Nach 20–25 Tagen wurde die Adultmasse erreicht; die Maximalmasse eines Kükens lag bei 193% der Adultmasse. Der Wachstumsverlauf der Küken wurde mit logistischen Gleichungen beschrieben.Signifikante geschlechtsspezifische Größenunterschiede der Altvögel ließen sich nur für die Flügellänge nachweisen. Die mittlere Ausbildung des Brutflecks der untersuchten Kolonie sank innerhalb einer fünfteiligen Skala von 3,7 (BF vollständig ausgebildet) während der Vorbrutzeit auf 1,4 (BF sehr gering ausgebildet) am Ende der Nestlingszeit.Vögel unterschiedlicher BF-Kategorien unterschieden sich in ihren Massen signifikant. Am Ende der Inkubationszeit wiesen nur noch Brüter einen gut ausgebildeten Brutfleck auf. Eine kombinierte Betrachtung von BF-Ausbildung und Masse läßt daher schon zu einem frühen Zeitpunkt verläßliche Rückschlüsse auf den Status eines Vogels (Brüter oder Nichtbrüter) zu. Am Ende der Brutsaison lag der so errechnete Nichtbrüter-Anteil bei 67%.

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Breeding and biometrics of Blackbellied Stormpetrel (Fregetta tropica) at King George Island, Antarctic

Summary During the austral summer of 1995/96 breeding aspects and biometrics of Blackbellied StormpetrelsFregetta tropica at King George Island, South Shetlands, were observed. The pre-laying period lasted until the end of December when the main laying time began. In the incubation period (duration 39–42 days) the breeding shifts of females and males were on average 1.6 and 1.8 days, respectively. Frequencies of breeding spells decreased dramatically towards the end of the incubation period. The chicks mainly hatched in the beginning/middle of February. Chick development was characterized by individually differing increases of body mass. After 20–25 days they reached adult body mass; the observed mass maximum was 109.9 g (193% of adult body mass). The development of body mass, wing length and tarsus length could be approximated using sigmoidal regression curves. 28 sexed adult birds showed significant differences only in wing length but not in tarsus length. From the pre-laying till the end of the hatching period the mean brood patch scores decreased from 3.7 (complete brood patch) to 1.4 (broodpatch weakly developed). Birds with well developed brood patches weighed on average 57.3 ± 4.0 g whereas birds with hardly visible brood patches weighed 53.5 ± 2.8 g. Because only breeders show brood patches at the end of the incubation period a consideration of both brood patchand body mass allows a reliable classification into breeders or nonbreeders. At the end of the hatching period 67% of all captured birds were nonbreeders.