首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Cesium-137 body burdens of Anaktuvuk Pass, Alaska, residents during the summer of 1965 were about 30 percent less than during 1964. Lower amounts of cesium-137 in the people reflected a similar decrease of this isotope in caribou flesh, which serves as the principal food of the natives.  相似文献   

2.
Reexamination of stratified faunal components of a prehistoric Aleut midden excavated on Amchitka Island, Alaska, indicates that Aleut prey items changed dramatically during 2500 years of aboriginal occupation. Recent ecological studies in the Aleutian Islands have shown the concurrent existence of two alternate stable nearshore communities, one dominated by macroalgae, the other by epibenthic herbivores, which are respectively maintained by the presence or absence of dense sea otter populations. Thus, rather than cultural shifts in food preference, the changes in Aleut prey were probably the result of local overexploitation of sea otters by aboriginal Aleuts.  相似文献   

3.
4.
DDE residues and eggshell changes in Alaskan falcons and hawks   总被引:1,自引:0,他引:1  
Eggshell thickness after exposure to DDT was reduced by 21.7 percent in Alaskan tundra peregrines, by 16.8 percent in taiga peregrines, by 7.5 percent in Aleutian peregrines, by 3.3 percent in rough-legged hawks, and not at all in gyrfalcons. Tundra peregrine eggs contain an average of 889 parts of DDE per million (lipid basis); taiga peregrine eggs contain 673 parts per million; Aleutian peregrine eggs contain 167 parts per million; rough-legged hawk eggs contain 22.5 parts per million; and gyrfalcon eggs contain 3.88 parts per million. These changes in eggshell thickness and the pesticide residues reflect different degrees of exposure to contamination. There is a highly significant negative correlation between shell thickness and DDE content in peregrine eggs. Tundra and taiga peregrines have fledged progressively fewer young each year since 1966.  相似文献   

5.
A study was made of the DDT and DDE content of the diet and body fat of native Alaskans who lived in isolated, primitive areas and had minimal contact with insecticides. No DDT or DDE was detected in any of the native Alaskan foods analyzed with the exception of two white owls, both of which contained low levels of DDE. Eskimos store considerably less DDT and DDE in their body fat than the general population in the United States. These low dietary levels and the resultant low levels in body fat are consistent with previously published data on the relationship between intake and storage of DDT.  相似文献   

6.
High-resolution analyses of lake sediment from southwestern Alaska reveal cyclic variations in climate and ecosystems during the Holocene. These variations occurred with periodicities similar to those of solar activity and appear to be coherent with time series of the cosmogenic nuclides 14C and 10Be as well as North Atlantic drift ice. Our results imply that small variations in solar irradiance induced pronounced cyclic changes in northern high-latitude environments. They also provide evidence that centennial-scale shifts in the Holocene climate were similar between the subpolar regions of the North Atlantic and North Pacific, possibly because of Sun-ocean-climate linkages.  相似文献   

7.
An original objective of these multidisciplinary studies was to determine the position of the Aleuts in the Aleutian ecosystem with time depth. This has been done in a variety of ways (7, 14, 20, 21). One of the most useful approaches is the construction of life expectancy tables. The greater longevity of Aleuts compared with Eskimos represents an effective biological and cultural human adaptation within this ecosystem. The Aleuts defined their ecosystem by expanding to the limits of the area they could effectively exploit with their complex technology, population structure, and population deployment system. Their intellectual achievements played a tangible role in their longevity in the pre-Russian period, and their sophisticated knowledge of human anatomy is both a causal and a consequential correlate of their longevity. From the Aleut point of view, the food resources were diverse, abundant, and accessible, and they also provided fabricational materials necessary for their complex material culture. The Aleuts successfully hunted the world's largest range of sea mammals, from the sea otter to the whales. At the same time, extensive use of invertebrates easily available on the ice-free strandflats enabled disadvantaged sectors of the population to make important contributions to their own food supply and thus improve life expectancy. The rich food and fabricational materials antedate the Holocene history of Nikolski Bay and the arrival of the ancestral Aleuts. The natural resources of this area are fundamentally related to the former peninsular extension of Beringia and the permanent upwelling system in Samalga Pass (22). Sea otters, seals, and sea lions were present when the first Aleuts came to the area. Nikolski Bay has been an ideal place to obtain samples representing the entire Holocene Epoch. The earliest Asiatic migrants came from Siberia and traversed the southern coastline of Beringia. They established a large and permanent village on the northern arm of Nikolski Bay and remained there while expanding to the far ends of the Aleutian domain in the sixth millennium of their residence. The record of cultural change spans a lithic revolution. It begins with a conservative unifacial core and blade industry that preserves several Asiatic traits but includes stone lamps, dishes, an image of the deity, and the use of red ochre. Between 7000 and 6000 years ago bifacially flaked and stemmed points appear, with some continuing elements of the old unifacial industry. This transition culture continues to about 4500 years ago, when the standard sequence seen in the old midden of Chaluka takes form. This culture continues, adding and subtracting various elements but always maintaining a distinctive configuration through time, to the present Aleuts, whose connection with the first Anangula settlement includes having remembered an older Aleut designation, "the place of the blades," and collecting eggs on its flanks. The dating of events inside Nikolski Bay and the identification of the Asiatic elements do throw light on human migration from Siberia into Alaska. The Aleuts and Eskimos may well have been a part of a single population system of Bering Sea Mongoloids who expanded along the Siberian coasts and across the southern Beringian coasts. The population that reached Nikolski Bay became Aleuts. Those closer to the old mouth of the Kuskokwim River and further north became Eskimos. The rise of sea level presented no problems to marine-adapted people. Instead it presented more opportunities in the form of more coastline to exploit. The ancestors of the American Indians migrated earlier through the interior of Beringia. The double-thumb hypothesis of Hrdlicka (23) is useful now for interpreting human migration into the New World. He suggested that if the Eskimos were physically related to the Indians as the thumb of one hand is to the fingers, then a second thumb is necessary to represent the Aleuts, who are also distinctive. The Bering Sea Mongoloids as a group (Aleuts, Eskimos, Chukchi, Koryaks, and probably Kamchadals) are distinguished from the Indians by both genetic traits such as the presence of blood group B, which is absent in the Indians, and morphological configurations such as the unusually broad, low ascending portions of the mandible. This magnitude of difference fits very well with a geographic difference in point of origin, separate route of entry into the New World across Beringia, and the maintenance of separation by many geographic, economic, and cultural barriers. Earlier investigators in the Aleutians compiled invaluable bodies of information. The Russian W. J. Jochelson worked in the Aleutians and the American A. Hrdlicka in Siberia. The problems common to both sides of the Bering Sea have now been studied by Soviet and American scholars at the same time, in the same place, and with the same specimens. It has been pleasant and informative to work directly with the Siberian authorities on Siberia in the Aleutians. In summary, I submit the following eight conclusions: 1) Increased longevity, rather than rapid population turnover, served as a major form of population adaptation and resource management among the Aleuts. Because people lived longer, genetic and cultural wastage was minimized. 2) Cranial vault change, from narrow to broad, has been the result of evolution within the population. 3) The Aleuts have continuously occupied Nikolski Bay, Umnak Island, for 8700 years. During this time sea level has risen and the coastline configuration has changed. 4) Siberian characteristics of the Anangula core and blade industry have been identified, and a transition culture, which links the earliest Anangula tool tradition with the later Aleut culture of Chaluka, has been discovered. 5) Organic remains of human occupation have been used to precisely date geological events of the Holocene Epoch for 8700 of its 10,000 years. Major volcanic eruptions occurred, at exponentially increasing intervals, 10,000, 9000, 7000 and 3000 years ago. 6) The earliest Aleut culture has preserved its Asiatic template because of the coastal entry route from Siberia and subsequent isolation of the population. The abundant lithic remains indicate a complex and diverse material culture. 7) The known similarity of Aleuts to Asiatic populations plus our Holocene time scale suggest a slower rate of human evolution than was assumed when a later date of entry into the Aleutians was accepted. 8) In the broadest perspective, these findings are relevant to understanding the entry of man (Aleuts, Eskimos, and Indians) into the New World in that other migrant populations originating in Siberia may also have entered the New World with a sophisticated and complex culture.  相似文献   

8.
Determination of the molecular structure and properties of allergens that elicit severe immediate-type hypersensitivity diseases in humans and a knowledge of the structure of their antibody-binding sites should provide new insight into the pathogenetic mechanisms of allergic diseases. Monomeric and homodimeric hemoglobins (CTT I to X) have been identified as potent allergenic components of Chironomidae, a family of Diptera. Immunologic investigations of peptides of three of these hemoglobins (CTT IV, CTT VI, and CTT VIII) showed that human antibodies of the E and G classes recognize at least two different sites within each molecule. Individual hemoglobin peptides were aligned with homologous regions of chironomid hemoglobin CTT III, whose tertiary structure has been determined by x-ray analysis at a resolution of 1.4 angstroms. The antigenic site CTT IV(91 to 101) showed the following characteristics: (i) seven polar or hydroxylated amino acids, from a total of eleven, occupying predominantly superficial regions; (ii) the property of linkage to other molecules by hydrogen bonds or solvent clusters; and (iii) high thermal mobility factors. In contrast, peptide CTT IV(102 to 108), which does not bind human antibodies, contained no polar amino acids and had low thermal mobility factors. These results support the idea that the antigenicity of clinically relevant proteins is related to regions with a predominance of polar amino acids and with low energy barriers between different conformations, which allow high flexibility, including site-specific adaptation in antibody binding.  相似文献   

9.
Polymerization of hemoglobins of mouse and man: structural basis   总被引:5,自引:0,他引:5  
  相似文献   

10.
Fetal mouse erythropoiesis proceeds initially in yolk-sac blood islands (8 to 12 days) and, subsequently, in liver (12 to at least 16 days). Yolksac cells synthesize three hemoglobins, Hb E(I), Hb E(II) and Hb E(III). Hb E(I) has x- and y-globin chains; Hb E(II) has alpha and y; HB E(III), alpha and z. No detectable beta-globin is formed in these cells. Liver erythroid cells form only adult hemoglobin, composed of alpha- and beta-chains.  相似文献   

11.
Agricultural development is an activity with many ethical problems. Nowhere are these problems more evident than in tropical forest regions, like the Amazon. This paper examines ethical issues associated with a particularly controversial activity in the region: pastures research. The paper discusses three general critiques of Amazonian agricultural development: ecological, social equity and cultural survival. A particular pastures research project is then examined. The paper concludes that pastures research can be an ethically sound activity when carried out in a manner that is sensitive to the social, cultural, and ecological context. The paper concludes that ethical decisions regarding agricultural research are context sensitive. A better appreciation of potential ethical dilemmas can be obtained by seeking participation by a variety of social actors in designing and carrying out agricultural research.  相似文献   

12.
Multiplicity of hemoglobins in the genus Chironomus (Tendipes)   总被引:2,自引:0,他引:2  
The number of hemoglobins found in individual mature larvae of several Chironomus species is six to nine. The consistency of this number and of the electrophoretic mobilities of these separable forms seems to indicate the synchronous production of polypeptide chains by several genetic loci.  相似文献   

13.
Electron exchange involving the valence states of iron occurs via water bridges. Molecular oxygen reversibly displaces the sole coordinated water of the ferrous iron in hemoglobin, and, in the absence of this ready path for electron transfer, the oxygen is transported without oxidation of the ferrous iron of hemoglobin.  相似文献   

14.
Indigenous ecologies in industrial societies need immediate attention in light of the ongoing debate on indigenous resource rights and decreasing biodiversity. This paper examines the functions and meanings of hunting, fishing, and gathering activities among contemporary Nez Perce Indians in Idaho, USA. The collected data were analyzed with Pierre Bourdieu's (1977) concepts of “symbolic capital” and “practice” within the framework of political ecology. The results clearly demonstrate that hunting, fishing, and gathering practices play significant roles not only in social and religious but also economic and political senses within the contemporary Nez Perce society. This study suggests that investigation of indigenous ecologies in industrial societies take a synthesized approach between idealist and materialist perspectives.  相似文献   

15.
Cerumen in American Indians: genetic implications of sticky and dry types   总被引:2,自引:0,他引:2  
Occurrence of sticky and dry cerumen was determined in 483 Indians from various tribes of the United States. The elevated frequencies of the allele for dry cerumen, found in Indians of pure ancestry, support the theory of the mongoloid origin of the American Indian. Potential application of cerumen quality as a marker for genetic and anthropological studies is discussed.  相似文献   

16.
In otherwise profoundly akinetic rats that had been severely depleted of brain catecholamines, anticholinergic drugs caused excessive walking. The effect did not appear until 10 days after surgery and then increased with time, suggesting that a phenomenon analogous to denervation supersensitivity may be involved. If the animals walked into corners, they were unable to turn around or back out. Their gait (extremely short steps) was reminiscent of that of patients with Parkinson's disease. The results are consistent with a mutually antagonistic interaction between cholinergic and dopaminergic brain systems and emphasize certain complexities in this interaction.  相似文献   

17.
18.
The cyanmet hybrid hemoglobins alpha(2)beta(+CN)(2) and alpha(+CN)(2)beta(2) are widely held to be similar or equivalent in structure and subunit interactions to the partially oxygen-liganded species alpha(2)(beta * O(2))(2) and (alpha * O(2))(2)beta(2), respectively. An analysis of precise data on oxygen binding to the cyanmet hybrids and normal hemoglobin shows that if this is the case, then cooperative ligand binding in hemoglobin is more properly described by some model of the sequential type than by any twostate concerted model.  相似文献   

19.
The dominant hemoglobin of the adult hamster was detected in yolk-sac erythroid cells, and its identity was confirmed by peptide mapping and by analysis of relevant peptides. Both the presence and active synthesis of two embryonic hemoglobins presumed to exist only in yolk-sac erythroid cells were detected in neonatal liver and spleen. Thus the time span of expression of both embryonic and adult globin genes during mammalian ontogeny may be considerably broader than presently believed.  相似文献   

20.
Sheep and goats switch from the synthesis of hemoglobin A (alpha(2)beta(2)(A)) to hemoglobin C (alpha(2)beta(2)(C)) when made anemic. We have demonstrated the existence of the asymmetrical hybrid hemoglobin, alpha(2)beta(A)beta(C), in the circulating red cells of anemic sheep. These erythroid cells, therefore, synthesized both A and C hemoglobin simultaneously. Thus, the switch appears to be mediated by selective gene expression rather than by a clonal or cellular selective mechanism.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号