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291.
Sergei Kan 《American anthropologist》2003,105(3):648-649
Against Culture: Development, Politics, and Religion in Indian Alaska. Kirk Dombrowski. Lincoln: University of Nebraska Press, 2001. 247 pp. 相似文献
292.
Koichi Matsuzaki Mikio Kan Wallace L. McKeehan 《In vitro cellular & developmental biology. Animal》1996,32(6):345-360
Summary Two transmembrane serine-threonine kinases (type I and II receptors), a membrane-anchored proteoglycan (type III), and a homodimeric
ligand participate in the transforming growth factor beta type on (TGFβ1) signal transduction complex. The expression of recombinant
receptors in insect cells co-infected with up to three recombinant baculoviruses was employed to study interactions among
the ectodomains of the three types of receptors and the TGFβ1 ligand in absence of uncontrollable extrinsic factors in mammalian
cells. Multi-subunit complexes were assembled in intact cells and purified on glutathione-conjugated beads for analysis by
tagging one of the subunits with glutathione S-transferase (GST). Intrinsic ligand-independent interactions were observed
among receptor subunits as follows: type III–III type I–I, type III-I, and type II-I. The homeotypic complex of type II–II
receptors and the heterotypic type III-II interaction was ligand dependent. The type I, but not the type III, subunit displaced
about 50% of the type II component in either ligand-dependent homomeric type II-type II complexes or heteromeric type III-type
II complexes to form type II-I or type III-II-I oligomers, respectively. The type II subunit displaced type I subunits in
oligomers of the type I subunit. Specificity of type I receptors may result from differential affinity for the type II receptor
rather than specificity for ligand. A monomeric subunit of the TGFβ1 ligand bound concurrently to type III and type II or
type III and type I receptors, but failed to concurrently bind to the type II and type I subunits. The binding of TGFβ1 to
the type I kinase subunit appears to require an intact disulfide-linked ligand dimer in the absence of a type III subunit.
The combined results suggest a pentameric TGFβ signal transduction complex in which one unit each of the type III, type II,
and type I components is assembled around the two subunits of the dimeric TGFβ1 ligand. An immobilized GST-tagged subunit
of the receptor complex was utilized to assemble multi-subunit complexesin vitro and to study the phosphorylation events among subunits in the absence of extrinsic cell-derived kinases. The results revealed
that (a) a low level of ligand-independent autophosphorylation occurs in the type I kinase; (b) a high level of autophosphorylation
occurs in the type II kinase; (c) both the type III and type I subunits aretrans-phosphorylated by the type II subunit; and (d) the presence of both type I and II kinases complexed with the type III subunit
and dimeric TGFβ1 ligand in a pentameric complex causes maximum phosphorylation of all three receptor subunits. 相似文献
293.
R. Schoysman B. Lejeune E. Van Roosendaal L. Segal P. Vanderzwalmen M. Nijs B. Vandamme G. Bertin 《Andrologie》1996,6(4):432-439
The authors report their experience with the use of spermatids in TESE programs where mature spermatozoa could not be isolated from testicular biopsies. The details of the indications for spermatid insemination, the technicity of the procedure and the results are exposed. 相似文献
294.
295.
Michael Garrick Donna Scott Susannah Walpole Eric Finkelstein Joy Whitbred Sandeep Chopra Lalitha Trivikram David Mayes Daphne Rhodes Kimberly Cabbagestalk Rahmi Oklu Adnan Sadiq Brett Mascia James Hoke Laura Garrick 《Biometals》1997,10(2):65-76
Belgrade rats inherit microcytic, hypochromic anemia as an autosomalrecessive trait (gene symbol b). Erythrocytes and tissue are iron deficientin the face of elevated TIBC (total iron binding capacity) and percent ironsaturation; iron injections increased the number of erythrocytes but theirappearance remained abnormal. We have investigated iron supplements toimprove husbandry of b/b rats and to learn more about the underlying defectand its tissue distribution. Weekly IM (intramuscular) injections ofiron–dextran (Imferon at 30 mg kg) improved the anemia but did not alter thered cell morphology. Certain diets also improved the health of b/b rats whencompared to standard rat chows by the criteria of weight, survival toadulthood, hematology and reproduction. The critical nutritional factorturned out to be iron bioavailability, with ferrous iron added to the dietimproving the health of Belgrade rats without affecting the underlyingerythroid defect. Tissue iron measurements after dietary or parenteralsupplementation confirmed the iron deficient status of untreated b/b rats andestablished that dietary ferrous iron partially relieved this deficiency,with injections leading to greater amounts of tissue iron. Serum iron andTIBC were also found to be elevated in untreated b/b rats, with dietarysupplementation decreasing but not eliminating the elevation in TIBC. Thesestudies indicate that iron supplements can improve the health of b/b ratswithout altering the underlying defect and also suggest that the mutationcould alter iron uptake in the GI (gastrointestinal) tract. 相似文献
296.
Extended models of the ventilatory response to sustained isocapnic hypoxia in humans 总被引:2,自引:0,他引:2
Liang, Pei-Ji, Daphne A. Bascom, and Peter A. Robbins.Extended models of the ventilatory response to sustained isocapnic hypoxia in humans. J. Appl. Physiol. 82(2): 667-677, 1997.The purpose of this study was to examine extensions of a modelof hypoxic ventilatory decline (HVD) in humans. In the original model (model I) devised by R. Painter, S. Khamnei, and P. Robbins(J. Appl. Physiol. 74: 2007-2015, 1993), HVD is modeledentirely by a modulation of peripheral chemoreflex sensitivity. In thefirst extension (model II), a more complicated dynamic is usedfor the change in peripheral chemoreflex sensitivity. In the secondextension (model III), HVD is modeled as a combination ofboth the mechanism of Painter et al. and a component that isindependent of peripheral chemoreflex sensitivity. In all cases, aparallel noise structure was incorporated to describe the stochasticproperties of the ventilatory behavior to remove the correlation of theresiduals. Data came from six subjects from a study by D. A. Bascom, J. J. Pandit, I. D. Clement, and P. A. Robbins (Respir. Physiol.88: 299-312, 1992). For model II, there was a significantimprovement in fit for two out of six subjects. The reasons for thiswere not entirely clear. For model III, the fit was againsignificantly improved in two subjects, but in this case the subjectswere those who had the most marked undershoot and recovery ofventilation at the relief of hypoxia. In these two subjects, thechemoreflex-independent component contributed ~50% to total HVD.In the other four subjects, the chemoreflex-independent componentcontributed ~10% to total HVD. It is concluded that in somesubjects, but not in others, there may be a component of HVD thatis independent of peripheral chemoreflex sensitivity. 相似文献
297.
A. Jagannadha Rao N. Mathialagan S. G. Kotagi N. R. Moudgal 《Journal of biosciences》1984,6(2):97-106
The regulation of secretion of chorionic gonadotropin in primates has been studied using bothin vivo andin vitro models.In vivo studies using the pregnant bonnet monkey revealed that at the doses tested, the administration of progesterone or estradiol 17Β in combination or alone did not result in any appreciable change in the duration or magnitude of serum chorionic gonadotropin levels. However, administration of lutropin-releasing hormone by intravenous route resulted in significant increase in chorionic gonadotropin levels within 30–60 min and the extent of stimulation seemed to depend on the state of pregnancy. Forin vitro studies, explants or cells prepared from first trimester human placenta has been used. The functional integrity of these cells has been established by demonstrating the binding of [125I]-labelled human chorionic gonadotropin antibody to the cells as well as the synthesis of [3H]-labelled human chorionic gonadotropin.In vitro studies using the cells revealed that addition of lutropin-releasing hormone caused a significant increase in chorionic gonadotropin and estradiol 17Β secreted into the medium. Thus bothin vivo andin vitro results suggest that lutropin-releasing hormone could be one of the factors involved in regulation of chorionic gonadotropin secretion in primates. 相似文献
298.
299.
Sequence of the 3''-noncoding and adjacent coding regions of human gamma-globin mRNA. 总被引:4,自引:4,他引:0 下载免费PDF全文
In cloning human fetal globin cDNA in bacterial plasmids, we obtained a recombinant which contained a fragment of gammg-globin cDNA corresponding to the region from amino acid 99 to the poly A. We determined a sequence of 169 nucleotides which included the complete 3' non-coding region of the gamma-globin mRNA. The codon for amino acid 136 was GCA, indicating that this cloned fragment was derived from the Agamma-globin gene. In conjunction with the surrounding sequences, the GCA codon provides the Agamma-species with a unique CTGCAG hexanucleotide that is recognized by the restriction enzyme Pst I. The 3'-untranslated region of the gamma-globin mRNA consists of 90 nucleotides, and shares little homology with that of the human beta-globin mRNA. As in other mammalian mRNAs, a symmetrical sequence and the hexanucleotide AAUAAA are present. 相似文献
300.
The degenerative changes in the spermatids as measured by changes in fine structure abnormalities increased with time following
injection of Cd2+ into rat testis. The spermatids in the twelve hours group appear as peculiarly club shaped and elongated structures with
one or two small but perceptible vacuoles. The subacrosomal area and the space between the nucleus and the middle piece are
seen abnormally dilated. In the 30 day group, the central filaments are the most susceptible unit of 9+2 axoneme complex.
The plasma membrane, the cytoplasmic matrix, the mitochondria of the middle piece and the fibrous sheath appear shrunken,
discontinuous and degenerative. 相似文献