Much study has already been devoted to the plumage of birds and its development, and the extensive literature to which this study has given rise might at first sight make it appear that no room is left for any new contributions to a subject which has already attracted so many investigators. The special branches of the subject, however, which have attracted most attention, have been:—(1) The histology of developing feathers, to which Studer, Davies, Wohlauer, and Bornstein have contributed; (2) pigmentation, investigated by STRONG; and (3) more recently what may be called the continuity between early “down” and adult feathers, a condition which does not appear to have been clearly realised before Jones and Gadow published the results of their researches. Recently also Waterston and Geddes, working on the embryology and anatomy of the Penguin, have touched incidentally on the appearance of down-papillæ and down at successive embryonic stages in the Penguin and the Duck; but, covering a wider field of research, they have not devoted to feather development in particular that careful observation and detailed study which the interest of the subject and the deficiencies of our knowledge appear to warrant.
For two centuries and a half the ampullary canal system of Elasmobranch fishes has occupied the attention of a series of investigators, who have treated the subject from a variety of standpoints, and have amassed a considerable literature representing, in spite of repetition and some conflicting statements, a gradual advance to a fuller knowledge regarding the occurrence and the structure of the organs in question.
. 2007. Stability of bovine milk progesterone under different storage and thawing conditions. Can. J. Anim. Sci. 87: 123-128. The objectives were to determine the effects of storage temperature (21 or 4°C), a preservative agent (Brotab 10 ® ) (exp. 1), thawing temperature (37, 21, or 4°C), repeated freeze-thaw cycles (exp. 2), and length of storage at -20°C (exp. 3) on the stability of bovine milk progesterone (P4) over an 8-wk period. Whole-milk samples of 19 pregnant dairy cows were analyzed for P4 using an enzymeimmunoassay (Quanticheck ® ). In exp. 1, mean P4 concentrations declined (P < 0.01) from 0 to 28 d (5.2 ± 0.1 vs. 3.3 ± 0.1 ng mL -1 ), but not any further at 56 d. However, P4 decline was lower (P < 0.01) at 4°C than at 21°C at 3 and 56 d, respectively (4.3 ± 0.1 and 3.8 ± 0.1 vs. 3.9 ± 0.1 and 3.0 ± 0.1 ng mL -1 ). Brotab 10 ® tended (P < 0.08) to reduce P4 decline. In exp. 2, thawing temperature and repeated freeze-thaw cycles, and in exp. 3, the length of storage at -20°C, did not greatly affect P4 stability. Regardless of the temperature, P4 concentrations declined in all experiments by 1.1 ± 0.1 mL -1 in the first 3 to 7 d of storage and remained relatively stable thereafter, except when stored at room temperature in the absence of a preservative agent. In conclusion, P4 in whole-milk samples remained relatively stable for up to 3 d at 21°C and for up to 14 d at 4°C, even in the absence of a preservative agent. For periods longer than 14 d, whole-milk samples are best stored at -20°C for optimum stability of P4. (première expérience), de la température de décongélation (37°C, 21°C ou 4°C) ou de cycles successifs de congélation et de décongélation (deuxième expérience) ainsi que de la durée de l'entreposage à -20°C (troisième expérience) sur la stabilité de la progestérone du lait de vache (P4) durant une période de huit semaines. Les auteurs ont analysé des échantillons de lait venant de 19 vaches gravides pour mesurer la quantité de P4 par dosage immunoenzymatique (Quanticheck ® ). Lors de la première expérience, la concentration moyenne de P4 a diminué (P < 0,01) entre le premier et le 28 e jour (5,2 ± 0,1 c. 3,3 ± 0,1 ng par mL) avant de se stabiliser jusqu'au 56 e jour. La réduction de la quantité de P4 était cependant plus faible (P < 0,01) à 4°C qu'à 21°C aux jours 3 et 56, respectivement (4,3 ± 0,1 et 3,8 ± 0,1 c. 3,9 ± 0,1 et 3,0 ± 0,1 ng par mL). Le Brotab 10 ® a tendance (P < 0,08) à atténuer la baisse de la concentration de P4. La température de décon-gélation et les cycles successifs de congélation/décongélation durant la deuxième expérience et la durée de l'entreposage à -20°C pendant la troisième n'affectent pas considérablement la stabilité de la P4. La concentration de P4 a diminué dans toutes les expéri-ences, peu importe la température, soit de 1,1 ± 0,1 ng par mL dans les 3 à 7 premiers jours de stockage avant de se stabiliser relativement par la suite, sauf quand le lait était entreposé à température ambiante, sans agent de conservation. En résumé, la concentration de P4 dans...
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