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111.
Stephen Collier 《American journal of physical anthropology》1993,91(4):485-504
Postcranial skeletal data from two recent Eskimo populations are used to test David Frayer's model of sexual dimorphism reduction in Europe between the Upper Paleolithic and Mesolithic. Frayer argued that a change from big-game hunting and adoption of new technology in the Mesolithic reduced selection for large body size in males and led to a reduction in skeletal sexual dimorphism. Though aspects of Frayer's work have been criticized in the literature, the association of big-game hunting and high sexual dimorphism is untested. This study employs univariate and multivariate analysis to test that association by examining sexual dimorphism of cranial and postcranial bones of two recent Alaskan Eskimo populations, one being big-game (whale and other large marine mammal) hunting people, and the second being salmon fishing, riverine people. While big-game hunting influences skeletal robusticity, it cannot be said to lead to greater sexual dimorphism generally. The two populations had different relative sexual dimorphism levels for different parts of the body. Notably, the big-game hunting (whaling) Eskimos had the lower multivariate dimorphism in the humerus, which could be expected to be the structure under greatest exertion by such hunting in males. While the exertions of the whale hunting economic activities led to high skeletal robusticity, as predicted by Frayer's model, this was true of the females as well as the males, resulting in low sexual dimorphism in some features. Females are half the sexual dimorphism equation, and they cannot be seen as constants in any model of economic behavior. © 1993 Wiley-Liss, Inc. 相似文献
112.
Neil C. Talbot Caird E. Rexroad Jr. Vernon G. Pursel Anne M. Powell Neil D. Nel 《In vitro cellular & developmental biology. Animal》1993,29(7):543-554
Summary Pig epiblast cells that had been separated from other early embryonic cells were cultured in vitro. A three-step dissection
protocol was used to isolate the epiblast from trophectoderm and primitive endoderm before culturing. Blastocysts collected
at 7 to 8 days postestrus were immunodissected to obtain the inner cell mass (ICM) and destroy trophectodermal cells. The
ICM was cultured for 2 to 3 days on STO feeder cells. The epiblast was then physically dissected free of associated primitive
endoderm. Epiblast-derived cells, grown on STO feeders, produced colonies of small cells resembling mouse embryonic stem cells.
This primary cell morphology changed as the colonies grew and evolved into three distinct colony types (endodermlike, neural
rosette, or complex). Cell cultures derived from these three colony types spontaneously differentiated into numerous specialized
cell types in STO co-culture. These included fibroblasts, endodermlike cells, neuronlike cells, pigmented cells, adipogenic
cells, contracting muscle cells, dome-forming epithelium, ciliated epithelium, tubule-forming epithelium, and a round amoeboid
cell type resembling a plasmacyte after Wright staining. The neuronlike cells, contracting muscle cells, and tubule-forming
epithelium had normal karyotypes and displayed finite or undefined life spans upon long-term STO co-culture. The dome-forming
epithelium had an indefinite life span in STO co-culture and also retained a normal karyotype. These results demonstrate the
in vitro pluripotency of pig epiblast cells and indicate the epiblast can be a source for deriving various specialized cell
cultures or cell lines. 相似文献
113.
Alan M. Goldberg John M. Frazier David Brusick Michael S. Dickens Oliver Flint Stephen D. Gettings Richard N. Hill Robert L. Lipnick Kevin J. Renskers June A. Bradlaw Robert A. Scala Bellina Veronesi Sidney Green Neil L. Wilcox Rodger D. Curren 《In vitro cellular & developmental biology. Animal》1993,29(9):688-692
Summary The development and application of in vitro alternatives designed to reduce or replace the use of animals, or to lessen the
distress and discomfort of laboratory animals, is a rapidly developing trend in toxicology. However, at present there is no
formal administrative process to organize, coordinate, or evaluate validation activities. A framework capable of fostering
the validation of new methods is essential for the effective transfer of new technologic developments from the research laboratory
into practical use. This committee has identified four essential validation resources: chemical bank(s), cell and tissue banks,
a data bank, and reference laboratories. The creation of a Scientific Advisory Board composed of experts in the various aspects
and endpoints of toxicity testing, and representing the academic, industrial, and regulatory communities, is recommended.
Test validation acceptance is contingent on broad buy-in by disparate groups in the scientific community—academics, industry,
and government. This is best achieved by early and frequent communication among parties and agreement on common goals. It
is hoped that the creation of a validation infrastructure composed of the elements described in this report will facilitate
scientific acceptance and utilization of alternative methodologies and speed implementation of replacement, reduction, and
refinement alternatives in toxicity testing. 相似文献
114.
115.
116.
Release of the cellular prion protein from cultured cells after loss of its glycoinositol phospholipid anchor 总被引:3,自引:0,他引:3
Borchelt David R.; Rogers Mark; Stahl Neil; Telling Glenn; Prusiner Stanley B. 《Glycobiology》1993,3(4):319-329
Secreted forms of the sialoglycoprotein designated cellularprion protein (PrPC) have been identified that cannot be explainedby alternative splicing. We report that secreted forms of PrPCderive from precursors that are bound to the plasma membraneby glycoinositol phospholipid (GPI) anchors. Secreted PrPC slowlyappeared in the culture medium of metabolically radiolabelledcells after incubations of 824 h. Digestion of nascentPrPC with phosphatidylinositol-specific phospholipase C (PIPLC)prevented the appearance of secreted PrPC. Secreted PrPc partitionedinto the aqueous phase of Triton X114 like PIPLC-releasedPrPC. While the Mr of PIPLC-released PrPC was reduced 24kDa after treatment with aqueous hydroflouric acid, which removesthe entire GPI anchor modification, the Mr of secreted PrPCwas unchanged. Both PIPLC-released and secreted PrPc were recognizedby antiserum raised against a synthetic C-terminal peptide correspondingto residues 220233 (amino acid 231 is the site of GPIattachment). We conclude that GPI-anchored PrPC is post-translationallyprocessed to remove most, if not all, of the GPI modificationand then shed into culture medium. Whether PrPC is shed afterproteolysis near the C-terminus remains to be established. Aminority of PrPC in normal Syrian hamster brain partitionedinto the aqueous phase of Triton X114 like shed PrPCsuggesting physiological significance. post-translational prion protein secretion sialoglycoprotein 相似文献
117.
118.
A series of mitochondrially inherited chloramphenicol-resistant (CAP-R) mutants were isolated in Chinese hamster cells. To determine whether the Chinese hamster CAP-R mutations were homologous to those isolated in mouse and human cell culture systems, we determined the nucleotide sequence of the region of the mitochondrial 16S rRNA gene spanning the peptidyl transferase-encoding region for eight CAP-R mutant lines in addition to the parental wildtype line. Three main conclusions are drawn from these studies. (1) Although the region of the gene encoding the peptidyl transferase domain is highly conserved relative to that of mice and rats, the contiguous sequences show less conservation. This sequence divergence not only includes the accumulation of single base pair replacements, but also the presence of small insertions or deletions. (2) For six of the CAP-R mutants, heteroplasmic single base pair changes were detected. These mapped to the same sites within the peptidyl transferase domain as the mutations found previously in mouse and human CAP-R mutants. (3) Two Chinese hamster CAP-R mutants, both with an unusual drug resistance phenotype, did not carry any mutations within the CAP-R peptidyl transferase domain. However, both carried a heteroplasmic mutation at the position corresponding to nucleotide 2505 of the mouse 16S rRNA gene, a site predicted to map within a stem/loop structure attached to this key domain of the ribosome. This is the first evidence for mitochondrial CAP-R mutations that map outside the peptidyl transferase region. 相似文献
119.
Ten crossbred, fourth or fifth parity sows were divided into 2 groups - high (H) and low (L) - according to their backfat thickness 9 days before parturition. Body weight, backfat thickness and litter weight were recorded repeatedly during a 5 week lactation period. The length of the interval from weaning to first oestrus was also noted. All sows were fed a commercial diet (11.9 MJ/kg, 14.5% crude protein). During gestation, daily food intake was 2.2 kg/sow, while during lactation it was 3.0 kg/sow plus 0.4 kg/piglet. Blood samples were drawn on day 9 before parturition and on days 2,7,14 and 21 of lactation. The samples were analysed to determine concentrations of glucose, urea nitrogen, creatinine, triglycerides, free fatty acids and beta-hydroxybutyric acid. In both groups, concentrations of free fatty acids and urea nitrogen were low on day 9 before parturition while those of triglycerides were high, indicating anabolism regardless of backfat thickness. During the first week of lactation, concentrations of free fatty acids increased in the H-group but not in the L-group, and concentrations of urea nitrogen were higher in the H-group. These differences, together with the greater loss of weight observed in the H-group, indicate that catabolism of maternal fat and protein depots was more pronounced in the Η-group than in the L-group during this time. On day 14 of lactation, both groups showed equally low concentrations of free fatty acids, decreasing creatinine concentrations and stable triglyceride and urea nitrogen concentrations. Furthermore, weight loss during the second and third weeks of lactation was low in both groups. These facts, taken together, indicate that the catabolic rate was decreasing in both groups during this period. No differences in return to oestrus interval were noted between the groups. The present study indicates that under a restricted feeding regime the catabolic rate during the first week of lactation is higher in sows with higher backfat thickness in late gestation. As lactation progresses, a more balanced metabolism is achieved regardless of backfat thickness, which may tend to reduce differences in return to oestrous interval. 相似文献
120.
Xindong Xu Yifeng Wang Changhong Wang Gangqiang Guo Xinyu Yu Yang Dai Yaobao Liu Guiying Wei Xiaohui He Ge Jin Ziqiu Zhang Qingtian Guan Arnab Pain Shengyue Wang Wenbao Zhang Neil D. Young Robin B. Gasser Donald P. McManus Jun Cao Qi Zhou Qingfeng Zhang 《Molecular ecology resources》2023,23(1):205-221