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排序方式: 共有460条查询结果,搜索用时 15 毫秒
451.
G. Billy 《Journal of human evolution》1975,4(6):517-520
It is shown that subjects born from marriages between individuals from different localities have a longer and narrower head, as well as a greater stature, than individuals whose parents were born in the same commune. The distance between the parents' birthplaces acts in the same way as the increasing size of the locality. Such results demonstrate that exogamy, in the widest meaning of the term, leads to cephalic and statural modifications of the same kind as those recorded for about a century among present day populations of western Europe. 相似文献
452.
Summary We compared the effects of 9.5 months of a continuous flooding treatment with a drained control treatment on one year-old
seedlings of green ash (Fraxinus pennsylvanica Marsh.) and water oak (Quercus nigra L.), two tree species common to the bottomland-hardwood forests of eastern North America. The internal root gas composition
of the more flood tolerant species, green ash, maintained higher oxygen and lower carbon dioxide concentrations under the
flooding treatment than water oak. This apparently resulted in differences in rhizosphere oxidation. The amounts of Fe and
Mn and the Fe/Mn ratio of the root coating extracted from trees in reduced soil conditions were much higher for the green
ash than the water oak. It is argued that this reflects differences in the ability of these two species to maintain rhizosphere
oxidation under prolonged periods of flooding and to prevent the accumulation of reduced potentially phytotoxic compounds.
Alcohol dehydrogenase activity increased in the green ash and decreased in the water oak in the flooded treatment. This indicated
that the better adapted species was able to rely upon increased anaerobic respiration in order to compensate for the decreased
root oxygen supply, but the water oak was unable to maintain previous levels of respiration, probably as the result of sulfide
toxicity. 相似文献
453.
A bioluminescence procedure for measurement of microbial ATP allows a rapid determination of the effectiveness of autoclave sterilization. This determination is achieved faster than detection of acid production in a biological indicator via a pH indicator. Bacterial outgrowth from spores on test strips of the biological indicator was detected by measurement of ATP using the firefly luciferase reaction. A measureable increase in ATP was found after 5 hours of incubation of a biological indicator that had been treated under sterilizing conditions that produced 75% sterility of the biological indicator as measured by acid production. This is a marked improvement over the 24-48 hours of incubation currently required. 相似文献
454.
455.
456.
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
457.
Beatriz Zayas-Rivera Lifang Zhang Stephen G. Grant Phouthone Keohavong Billy W. Day 《Biomarkers》2013,18(4):262-273
4-Aminobiphenyl is a human bladder carcinogen present in many environmental sources, including cigarette smoke. It can be metabolized in two steps to the mutagen N-hydroxy-N-acetyl-4-aminobiphenyl (N-OH-AABP). In this study the mutational spectrum of N-OH-AABP-exposed human lymphoblastoid cells (TK6) was determined using HPRT 相似文献
458.
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
459.
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
460.
Christopher F. Cummings Vadim Pedchenko Kyle L. Brown Selene Colon Mohamed Rafi Celestial Jones-Paris Elena Pokydeshava Min Liu Jose C. Pastor-Pareja Cody Stothers Isi A. Ero-Tolliver A. Scott McCall Roberto Vanacore Gautam Bhave Samuel Santoro Timothy S. Blackwell Roy Zent Ambra Pozzi Billy G. Hudson 《The Journal of cell biology》2016,213(4):479-494
Basement membranes are defining features of the cellular microenvironment; however, little is known regarding their assembly outside cells. We report that extracellular Cl− ions signal the assembly of collagen IV networks outside cells by triggering a conformational switch within collagen IV noncollagenous 1 (NC1) domains. Depletion of Cl− in cell culture perturbed collagen IV networks, disrupted matrix architecture, and repositioned basement membrane proteins. Phylogenetic evidence indicates this conformational switch is a fundamental mechanism of collagen IV network assembly throughout Metazoa. Using recombinant triple helical protomers, we prove that NC1 domains direct both protomer and network assembly and show in Drosophila that NC1 architecture is critical for incorporation into basement membranes. These discoveries provide an atomic-level understanding of the dynamic interactions between extracellular Cl− and collagen IV assembly outside cells, a critical step in the assembly and organization of basement membranes that enable tissue architecture and function. Moreover, this provides a mechanistic framework for understanding the molecular pathobiology of NC1 domains. 相似文献