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551.
G. Billy 《Journal of human evolution》1980,9(8):591-595
The skeletal remains from the cave of the Figuier are believed now to be of Magdalenian date. They belong to a three year old child. Though the mandible and the dentition show some archaic morphological trends, the majority of the characters are not essentially different from those of modern children of the same age living now. These remains must be related to Homo sapiens sapiens. 相似文献
552.
The in vitro production of hemolysin byListeria monocytogenes, a facultative intracellular bacterial pathogen, was examined as a function of medium iron. There was an inverse relationship between iron and hemolysin production: Hemolysis increased as medium iron concentration decreased. This study offers the first evidence that the in vitro production of hemolysin byListeria monocytogenes is under the control of external iron in growth medium. 相似文献
553.
Cnemidophorus uniparens is a parthenogenetic unisexual species of lizard in which each individual develops as a female, making it a unique animal model for the study of sexual differentiation. In one study, administration of exogenous testosterone before and/or after hatching influenced the development of the gonads, the accessory reproductive ducts, the renal sex segment of the mesonephric kidney, and the femoral glands, a secondary sex character. Testosterone treatment also affected the cross-sectional area of the gonad and the proportions of cortical and medullary tissues present in the developing gonad. The oviducts and femoral glands of testosterone-treated individuals were hypertrophied; the collecting tubules of the kidney of these animals contained granules, an androgen-dependent, sexually dimorphic character in squamate reptiles. In another study, testosterone, dihydrotestosterone, or estradiol were administered to C. uniparens embryos. No treatment effects on gonadal development were detected on the day of hatching. However, estradiol, but not testosterone and dihydrotestosterone, stimulated development of the oviducts. Taken together these studies suggest that androgen aromatization may play a role in sexual differentiation in lizards. 相似文献