共查询到20条相似文献,搜索用时 0 毫秒
1.
某些源自外胚层的骨外实体瘤,它们并未浸润至骨组织,但可引起血钙显著增高,提示这些肿瘤可能分泌体液因子作用于骨导致溶骨。我们从人膀胱癌、大鼠乳腺癌(Walker 256)及7.12-Dimethyl Benz[α]anthracene诱发的小鼠鳞癌的提取液中初步分离鉴定了一种溶骨因子。肿瘤提取液经ultrogel层析,发观仅有一溶骨活性峰(~(45)Ca自乳鼠顶骨培养中的释出率),相当于表观分子量15,000道尔顿。此溶骨活性峰与PGE2生成的活性峰相平行,两者均能被Indomethacin及煮沸所抑制。在膀胱癌及鳞癌中,溶骨活性峰还与刺激大鼠成骨肉瘤细胞腺苷酸环化酶的活性相平行。实验结果表明此溶骨因子不同于其它已知能引起溶骨的因子。 相似文献
2.
3.
4.
5.
6.
7.
Paul F. Parakkal 《The Journal of cell biology》1969,41(1):345-354
8.
9.
植物营养转移研究进展 总被引:11,自引:0,他引:11
50年代初 ,Gregory(见 Williams〔1〕)发现禾谷类植物在生长到其 (干 )生物量的 2 5%时 ,它就吸收积累了全部所需氮磷养分的 90 % ,这些积累的养分是后期生长发育所需的基本养分库 ,养分库的大小决定了产量的高低 ,无疑 ,这些养分必然在体内不断地转移、利用和再分配。这一发现立即引起极大的重视 ,并带来了大量以营养转移为主题的后续研究 ,直至最近的 2 0多年 ,这一主题仍然得到广泛的重视。大量的研究表明 ,营养转移是植物所有保持营养机制中最重要的策略之一 ,因而 ,它又对竞争、营养吸收、生产力等过程产生影响 〔2〕;它在植物体内营… 相似文献
10.
11.
《Ibis》1968,110(2):217-221
Balfour , E., Anderson , A. & Dunnet , G. M. 1967. Orkney Cormorants—their breeding distribution and dispersal. Bernis , F. 1966. El Buitre Negro Aegypius monachus en Iberia. Boase , H. 1965. Movements of the Mute Swan in East Scotland. Boylan , P. J. 1967. Western Atlantic Fulmars on the East Yorkshire coast. Bray , R. P. 1966. Progress report on the Pheasant Study, 1965. Brown , L. H. 1965. Redwinged starlings of Kenya. Brown , L. H. 1965. Observations on Verreaux's Eagle Owl Bubo lacteus (Temminck) in Kenya. Caldwell , L. D. 1964. Dove production and nest-site selection in southern Michigan. Campbell , B. 1965. The Crested Tit. Forestry Commission leaflet No. 41. Dowsett , R. J. 1967. Breeding biology of Lamprotornis mevesii (Wahlberg). Evans , P. R. 1966. Some results from the ringing of Rock Pipits on Skokholm, 1952–65. Harris , S. W., Morse , M. A. & Longley , W. H. 1963. Nesting and production of the Mourning Dove Zenaidura macroura in Minnesota. Hewson , R. 1967. The Rock Dove in Scotland in 1965. Hilden , O. 1965. Zur Brutbiologie des Temminckstrandlaüfers Calidris temininckii (Leisl.). Lind , E. A. 1964. Nistzeitliche Geselligkeit der Mehlschwalbe Delichon u. urbica Macdonald , D. 1965. Notes on the Corn Bunting in Sutherland. Macmillan , A. T. 1965. The Collared Dove in Scotland. Nelson , J. B. 1964. Some aspects of breeding biology and behaviour of the North Atlantic Gannet on the Bass Rock. Newton , I. 1964. The breeding biology of the Chaffinch. Nickell , W. P. 1965. Habitats, nesting, and territory of the Catbird. Nyholm , E. S. 1965. Ecological observations on the geese of Spitzbergen. Pinder , R. 1966. The Cape Pigeon Duption capensis Linnaeus at Signy Island, South Orkney Iskands. Richdale , L. E. 1965. Biology of the birds of Whero Island, New Zealand, with special reference to the Diving Petrel and the White-faced Storm Petrel. Rogers , J. P. & Korschgen , L. J. 1966. Foods of Lesser Scaups on breeding, migration and wintering areas. RYDER, J. P. 1967. The breeding biology of Ross' Goose in the Perry River region, Northwest Territories. Sandeman , G. L. 1963. Roseate and Sandwich Tern colonies in the Forth and neighbouring areas. Siegfried , W. R. 1967. The distribution and status of the Black Stork in southern Africa. Soikkeli , M. 1964. The distribution of the Southern Dunlin Calidris alpina schinzii in Finland. Speidel , G. 1966. Adelie Penguins in the Milwaukee County Zoo. Suetens , W. & Groenendael , P. Van . 1966. Ecología y conducta reproductora del Buitre Negro Aegypius monachus. Taylor , W. K. 1966. Additional records of Black-tailed Gnatcatchers Polioptila melanura parasitized by the dwarf-headed cowbird Molothrus ater Valverde , J. A. 1966. Sobre Buitres Negros en Andalucia. Waters , W. E. 1963. Observations on the Fulmar at St. Kilda. Waters . W. E. 1964. Observations on small petrels at St. Kilda. 1961–62. Scott. 相似文献
12.
13.
14.
An electron microscopic study of the tibial epiphyseal plates of growing rats reveals that the resorption of unmineralized and mineralized cartilage occurs by two different mechanisms. During resorption the unmineralized transverse cartilaginous walls between chondrocytes are invaded by capillary sprouts. At the resorption zone, numerous cytoplasmic processes derived primarily from the perivascular cells and, to a lesser extent, from the endothelial cells of the sprouts penetrate and appear to lyse the unmineralized transverse cartilaginous walls. Hydrolases released from the degenerating chondrocytes and/or capillary sprouts may also participate in this process. The second resorption mechanism involves the mineralized longitudinal cartilaginous septa. Resorption of these septa is mediated by chondroclasts whose fine structure is identical with that of osteoclasts. The active surface of the chondroclasts has a ruffled border. The surface membrane of the chondroclasts is relatively smooth on either side of the ruffled border and lies in direct apposition with the underlying mineralized cartilage. This observation suggests that the microenvironment in the zone of resorption may be maintained by the neighboring unruffled surfaces of the chondroclasts, which thus seal off and segregate the active portions of these cells. 相似文献
15.
16.
生物入侵的进化生物学 总被引:17,自引:0,他引:17
生物入侵(Biological invasion) 是指一种生物在人类活动的影响下,从原产地进入到一个新的栖息地,并通过定居(Colonizing) 、建群( Establishing) 和扩散(Diffusing) 而逐渐占领该栖息地,从而对当地土著生物和生态系统造成负面影响的一种生态现象。
相似文献
17.
18.
THE BIOLOGY OF PUBERTY 总被引:1,自引:0,他引:1
F. H. BRONSON EMILIE F. RISSMAN 《Biological reviews of the Cambridge Philosophical Society》1986,61(2):157-195
The objective of this review was to develop a broader, more biological, overview of puberty, as opposed to the more limited, laboratory-dominated, view that has emanated from experimental physiology. Three conceptual schemes form the basis for our broader perspective. The first deals with the ways in which genes and environmental factors interact to program the timing of reproductive development. The second focuses on the ways environmental factors interact with each other to influence puberty. The third relates the genetic and environmental controls to specific endocrine and neuroendocrine pathways of action.
The more traditional approach of studying domesticated animals under carefully controlled conditions predetermines one's conclusions. One logically will conclude that the final stages of reproductive development are rather rigidly determined genetically and not greatly subject to environmental regulation, except for obviously adaptive pheromonal and photoperiodic regulation. One also will search within the reproductive axis itself for the final developmental step that allows functional fertility. In contrast, a more biological view suggests that for most mammals puberty is a highly labile process subject to several kinds of environmental influences that operate at many times during a mammal's life. Furthermore this perspective suggests that the final developmental step allowing fertility onset normally will occur outside rather than within the reproductive axis proper. This conclusion has a potentially great impact upon the way we look at the organization of the brain and endocrine system and in the way we choose animal models for studying human puberty and the types of controls we study. 相似文献
The more traditional approach of studying domesticated animals under carefully controlled conditions predetermines one's conclusions. One logically will conclude that the final stages of reproductive development are rather rigidly determined genetically and not greatly subject to environmental regulation, except for obviously adaptive pheromonal and photoperiodic regulation. One also will search within the reproductive axis itself for the final developmental step that allows functional fertility. In contrast, a more biological view suggests that for most mammals puberty is a highly labile process subject to several kinds of environmental influences that operate at many times during a mammal's life. Furthermore this perspective suggests that the final developmental step allowing fertility onset normally will occur outside rather than within the reproductive axis proper. This conclusion has a potentially great impact upon the way we look at the organization of the brain and endocrine system and in the way we choose animal models for studying human puberty and the types of controls we study. 相似文献
19.
Leonard B. Thien 《American journal of botany》1974,61(10):1037-1045
The floral biology of eight species of Magnolia native to the United States is described. The flowers are protogynous. They are pollinated by several species of beetles that enter buds as well as closed and open flowers to feed on nectar, stigmas, pollen, and secretions of the petals. Individual flowers persist from two to four days and undergo a series of petal, stigma, and stamen movements that assure pollination by beetles. It is suggested that the flowers of Magnolia are highly specialized for exclusive pollination by beetles. These specialization mechanisms produce large quantities of food for the beetles and deny other types of insects (bees, moths, etc.) access to the flowers at critical stages in the pollination process, i.e., when stigmas are mature and pollen is shed. 相似文献
20.