930 resultados para level scheme of I-127


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Oocysts of Eimeria funduli were studied by transmission electron microscopy in naturally-infected livers of the Gulf killifish, Fundulus grandis. Tissues were cryo-processed because membranous structures in the oocyst appear to hinder routine fixation and embedment. The oocyst wall (about 25 nm thick) was adjacent to the host cell and consisted of an outer membrane that limited the host cell cytoplasm and an inner membrane separated from the outer membrane by a narrow space. In some specimens, dense material was applied to the inner face of the inner membrane. Individual sporocysts were surrounded by a membranous "veil" (about 25 nm thick) that consisted of two unit membranes. Sporopodia, projections of the sporocyst wall, supported the veil. The sporocyst wall (130-150 nm thick) consisted of two layers, a thin electron-lucent outer layer (about 10 nm thick) and a thick electron dense inner layer (about 130 nm thick). Depending on the plane of section, the inner layer had transverse striations with periods of 3 to 4 nm or 12 to 15 nm. A narrow fissure, broadest at the anterior pole of the sporocyst, extended about one-third the length of the sporocyst wall. The posterior pole of the sporocyst was characterized by a bulbous swelling. Although this swelling resembled a Stieda body in light microscopic preparations, ultrastructurally, the swelling was a knoblike thickening in the sporocyst wall and did not plug a gap in this wall

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The interface between stages of Eimeria funduli and hepatocytes of the experimentally infected killifish Fundulus similis was studied ultrastructurally. Parasitophorous vacuoles (PV's) in which meronts, macrogamonts, and microgamonts developed were lined by an inner, smooth membrane and an outer, ribosome-studded membrane. The outer membrane bordered on the cytoplasm of the host cell, whereas the inner one limited the PV. The origins of these membranes have not been determined with certainty, but images were observed in which both membranes appeared to be continuous with the outer nuclear membrane of the host cell. Furthermore, the outer PV membrane was continuous with membranes of rough endoplasmic reticulum in the host cell. For stages which were rapidly growing or differentiating, the inner membrane blebbed into the PV. Blebbing ceased and ribosomes detached from the outer membrane after maturation of the meront or fertilization of the macrogamont. Blebbing appears to be a mechanism by which nutrients transfer from the host to the parasite. During sporogony, the inner PV membrane acquired a thin layer of electron dense material, but otherwise membranes lining the PV remained intact. The two PV membranes, probably together with dense material of parasitic origin lining the inner membrane, appear to serve as the oocyst wall enclosing the sporocysts until they are released in the intermediate host.

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Although Lewis and Clark literature has proliferated in the last decade, few works have added scholarly discourse to this field of study. The highly focused Venereal Disease and the Lewis and Clark Expedition, however, will likely stand out on the Lewis and Clark bookshelf as an important contribution.

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The field of archaeology incorporates a confusing assortment of ideas and approaches to the record. With studies ranging widely in ideology and goals, from strict descriptive materialism to sociological interpretation, language used to communicate key concepts (not to mention which concepts are key) also varies widely, resulting in low levels of mutual interest and intelligibility across the discipline. Archaeologists commonly ignore the majority of available literature as a result, further widening intellectual chasms.

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Nomadic Plains peoples such as the Cheyenne and Sioux have become the stereotypical image of North American Indians in general. In contrast to the hunting and gathering lifestyle of these groups, however, many Plains tribes lived in settled villages and grew extensive garden crops through much of the past millennium. These groups developed a habitation distinctly characteristic of the Plains village way of life-sturdy, earth-covered timber structures known as earth lodges. The remains of thousands of these structures dot the landscape of the Central and Northern Plains. Lodges of various forms persisted from about 1000 CE into the twentieth century. Particularly characteristic of the Pawnee, Arikara, Mandan, and Hidatsa, earthlodges were also adopted by several other Plains tribes. In this well-illustrated volume eight authors offer nine essays that explore the earth lodge as a subject warranting archaeological and anthropological research in its own right and from numerous perspectives.

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Liz Bryan begins her book with a description of the Canadian Plains:" . .. a voluptuous landscape of hills and valleys and plains, of lakes and tiny twinkling potholes, of flower-filled coulees and vast sand dunes." Her emphasis throughout on the landscape of southern Saskatchewan and Alberta is necessary since the ancient monuments she describes only truly resonate within this setting. Indeed, almost every page of this attractive book is adorned with at least two color images-of scenery, stone features, artifacts, and aboriginal events. She then proceeds to an eclectic overview of the archaeological record of the Plains of Saskatchewan and Alberta, including the earliest human evidence, such as the Clovis points from the Wally's Beach site, Alberta, where the trackways of mammoths, camels, and muskoxen were miraculously and briefly exposed in the late 1990s. There is one perplexing error, however-the attribution of the extinction of the ice age bestiary, about 12,000 years ago, to the meteorite that felled the dinosaurs!

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If readers of Great Plains Research are seeking a window on rock art research in North America, this book provides a few clear panes, a few that are hazy, and a few muddy ones. Like many edited volumes, the weaker contributions and lack of a consistent style limit the book's usefulness. Some authors target a general readership; others clearly are addressing colleagues. The book has two stated themes: the history of rock art research in North America and recent approaches to rock art analysis. Articles by Julie Francis and (jointly) David Whitley and Jean Clottes explore why rock art research has long been marginalized in North America. Unfortunately, both of these otherwise observant essays slip into advocacy of shamanism as a unifying or primary explanation for rock art, an interpretive model by no means universally accepted by today's rock art specialists.

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The passage of the Native American Graves Protection and Repatriation Act (NAGPRA) in 1991 significantly changed the way archaeology would be done in the United States. This act was presaged by growing complaints and resentment directed at the scientific community by Native Americans over the treatment of their ancestral remains. Many of the underlying issues came to a head with the discovery and subsequent court battles over the 9,200-year-old individual commonly known as Kennewick Man. This had a galvanizing effect on the discipline, not only perpetuating the sometimes adversarial relationship between archaeologists and Native Americans, but also creating a rift between those archaeologists who understood Native American concerns and those who saw their ancestral skeletal remains representing the legacy of humankind and thus belonging to everyone. Similar scenarios have emerged in Australia.

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Applying ecological studies to the adaptations of prehistoric human hunter-gatherer groups has greatly increased our abilities to interpret effects of an ever-changing environment and our access to critical resources on these populations. The Pleistocene/Holocene transition, its climate and human genesis in the new world, draws intensive interest from a number of scientific communities. In Twilight of the Mammoths, Paul Martin adds his views, which are of no surprise, on the megafaunal extirpations during a cultural period referred to in North America as Clovis.

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Just as there are seashells on Mt. Everest, there is an exceptional wealth of fossil remains of marine organisms preserved in the chalk of western Kansas. This Cretaceous-aged rock, and the fossils therein, were deposited at a time when a great sea cut northward across the interior of the continent around 85 million years ago, inspiring the provocative title of Everhart's book. The title is true to its subject: documentation of the Cretaceous fossils of western Kansas, their geographic and stratigraphic occurrences, and the inferences that paleontologists can make about how the organisms represented by these fossils may have once lived and interacted with one another.

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As an extension vegetable specialist with a strong interest in organic farming and in assisting farmers to make a living, I relished this book. Leslie Duram is a geographer at Southern Illinois University Carbondale who has her roots in Kansas and is motivated by a love for Plains agriculture. The book, which she describes as a piece of advocacy scholarship, is at once scholarly, informative, and entertaining. In six well-organized chapters Duram provides an overview of organic farming within the context of overall U.S. agriculture and society (with our growing demand for organic food), reviews research describing organic farms and farmers , presents and analyzes the stories of five successful organic family farms, and offers a vision of a future American agriculture based on medium-sized organic family farms.

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Raising Less Corn, More Hell may sound like a rallying cry for the nation's heartland farmers, but this well-written series of essays by George Pyle is meant for those who eat corn. Or rather, for those of us who eat the livestock fed on corn in confined animal feeding operations, then wash down those meals with drinks high in high-fructose corn syrups. Pyle, an editorial writer from Kansas now living in Utah, brings his journalist's skills to bear on what our industrial food system has brought us. It's not appetizing as he makes his case against a corporate-controlled system that doesn't have to be this way.

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Thundering herds of bison have become synonymous with the pre-European colonization of the Great Plains. As such, they have captured the imagination of countless people, including Wes Olson, a 20-year warden for Parks Canada. Throughout Portraits of the Bison, based on both existing literature and the author's extensive experience observing and managing these animals, Olson's bison fascination is not only obvious but infectious. A remarkably talented artist as well, Olson's line drawings appear throughout the book, accompanied by Johane Janelle's photographs.

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Though intended as a field guide to the birds of the Great Plains, this book seems to serve best as a general introduction to Great Plains birds and will mostly benefit those casually interested in birds. The definition of Great Plains the book uses is rather broad, and some species are included that, in my opinion, aren't really birds of the Great Plains. For example, several warblers are included as breeding species although they nest within the book's definition of the region only in the conifer or mixed forest of north-central to northwestern Minnesota, which isn't really a part of the Great Plains proper.

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Dragonflies are beautiful animals, important predators in and around aquatic environments, and often good indicators of ecosystem health. Stimulated by digital photography, close-focusing binoculars, and many new regional field guides, the study of dragonflies has exploded in the last ten years. Most importantly, the Internet has connected beginners with experts; observers from everywhere now share their experiences. Here is a book that puts it all on paper.