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排序方式: 共有189条查询结果,搜索用时 31 毫秒
11.
Although the impact of blood parasite infections on passerine birds is potentially great, little is known of their pathologic effects. We studied Haemoproteus danilewskyi in experimentally infected captive and naturally infected free-ranging blue jays (Cyanocitta cristata) to determine patterns of infection and examine the pathologic effects of the parasite on the host. Physiologic changes, such as elevated numbers of lymphocytes, heterophils, basophils, eosinophils, and monocytes and decreased packed cell volume in the peripheral blood were associated with the erythrocytic phase of experimental infections of captive juvenile jays. Sublethal pathologic changes associated with the pre-erythrocytic phase of infections were observed in the liver, lung, and spleen. Schizonts were observed in the pulmonary capillaries of a 1 yr old jay necropsied 31 days post-inoculation, but not in 20 juvenile jays necropsied 57 days post-inoculation. In free-ranging naturally infected jays plasma protein concentration increased with density of natural infections. 相似文献
12.
The Role of Iron-Deficiency Stress Responses in Stimulating
Heavy-Metal Transport in Plants 总被引:30,自引:0,他引:30 下载免费PDF全文
Plant accumulation of Fe and other metals can be enhanced under Fe deficiency. We investigated the influence of Fe status on heavy-metal and divalent-cation uptake in roots of pea (Pisum sativum L. cv Sparkle) seedlings using Cd2+ uptake as a model system. Radiotracer techniques were used to quantify unidirectional 109Cd influx into roots of Fe-deficient and Fe-sufficient pea seedlings. The concentration-dependent kinetics for 109Cd influx were graphically complex and nonsaturating but could be resolved into a linear component and a saturable component exhibiting Michaelis-Menten kinetics. We demonstrated that the linear component was apoplastically bound Cd2+ remaining in the root cell wall after desorption, whereas the saturable component was transporter-mediated Cd2+ influx across the root-cell plasma membrane. The Cd2+ transport system in roots of both Fe-deficient and Fe-sufficient seedlings exhibited similar Michaelis constant values, 1.5 and 0.6 μm, respectively, for saturable Cd2+ influx, whereas the maximum initial velocity for Cd2+ uptake in Fe-deficient seedlings was nearly 7-fold higher than that in Fe-grown seedlings. Investigations into the mechanistic basis for this response demonstrated that Fe-deficiency-induced stimulation of the plasma membrane H+-ATPase did not play a role in the enhanced Cd2+ uptake. Expression studies with the Fe2+ transporter cloned from Arabidopsis, IRT1, indicated that Fe deficiency induced the expression of this transporter, which might facilitate the transport of heavy-metal divalent cations such as Cd2+ and Zn2+, in addition to Fe2+. 相似文献
13.
John P. Vogel David F. Garvin Oymon M. Leong Daniel M. Hayden 《Plant Cell, Tissue and Organ Culture》2006,84(2):100179-100191
Brachypodium distachyon (Brachypodium) has been proposed as a model temperate grass because its physical, genetic, and genome attributes (small stature, simple
growth requirements, small genome size, availability of diploid ecotypes, annual lifecycle and self fertility) are suitable
for a model plant system. Two additional requirements that are necessary before Brachypodium can be widely accepted as a model system are an efficient transformation system and homogeneous inbred reference genotypes.
Here we describe the development of inbred lines from 27 accessions of Brachypodium. Determination of c-values indicated that five of the source accessions were diploid. These diploid lines exhibit variation
for a variety of morphological traits. Conditions were identified that allow generation times as fast as two months in the
diploids. An Agrobacterium-mediated transformation protocol was developed and used to successfully transform 10 of the 19 lines tested with efficiencies
ranging from 0.4% to 15%. The diploid accession Bd21 was readily transformed. Segregation of transgenes in the T
1 generation indicated that most of the lines contained an insertion at a single genetic locus. The new resources and methodologies
reported here will advance the development and utilization of Brachypodium as a new model system for grass genomics. 相似文献
14.
Wang H D'Ambrosio MA Garvin JL Ren Y Carretero OA 《American journal of physiology. Renal physiology》2012,302(10):F1300-F1304
Tubuloglomerular feedback (TGF) and connecting tubule glomerular feedback (CTGF) are mechanisms that control afferent arteriole (Af-Art) tone. TGF, initiated by increased NaCl at the macula densa, causes Af-Art constriction. Prolonged activation of TGF leads to an attenuation or "resetting" of its constrictor effect. The mechanisms of TGF resetting remain incompletely understood. CTGF is initiated by increased NaCl in the connecting tubule and Na(+) entry via epithelial sodium channels (ENaC). Contrary to TGF, CTGF dilates the Af-Art. Here, we hypothesize that CTGF, in part, mediates TGF resetting. We performed micropuncture of individual rat nephrons while measuring stop-flow pressure (P(SF)), an index of glomerular filtration pressure and Af-Art tone. Increases in Af-Art tone cause P(SF) to decrease. TGF responses, measured as the decrease in P(SF) induced by switching late proximal tubule perfusion from 5 to 40 nl/min, were elicited before and after a 30-min period of sustained perfusion of the late proximal tubule at a rate of 40 nl/min designed to induce TGF resetting. TGF responses were 7.3 ± 0.3 and 4.9 ± 0.2 mmHg before and after resetting was induced (P < 0.001, n = 6). When CTGF was inhibited with the ENaC blocker benzamil (1 μM), TGF responses were 9.5 ± 0.3 and 8.8 ± 0.6 mmHg (NS, n = 6), thus resetting was abolished. In the presence of the carbonic anhydrase inhibitor acetazolamide (10 mM), TGF responses were 8.8 ± 0.6 and 3.3 ± 0.4 mmHg before and after resetting (P < 0.001, n = 6). With both acetazolamide and benzamil, TGF responses were 10.4 ± 0.2 and 8.4 ± 0.5 mmHg (P < 0.01, n = 6), thus resetting was attenuated. We conclude that CTGF, in part, mediates acutely induced TGF resetting. 相似文献
15.
Cui Y Lee MY Huo N Bragg J Yan L Yuan C Li C Holditch SJ Xie J Luo MC Li D Yu J Martin J Schackwitz W Gu YQ Vogel JP Jackson AO Liu Z Garvin DF 《PloS one》2012,7(6):e38333
The ND18 strain of Barley stripe mosaic virus (BSMV) infects several lines of Brachypodium distachyon, a recently developed model system for genomics research in cereals. Among the inbred lines tested, Bd3-1 is highly resistant at 20 to 25 °C, whereas Bd21 is susceptible and infection results in an intense mosaic phenotype accompanied by high levels of replicating virus. We generated an F(6:7) recombinant inbred line (RIL) population from a cross between Bd3-1 and Bd21 and used the RILs, and an F(2) population of a second Bd21 × Bd3-1 cross to evaluate the inheritance of resistance. The results indicate that resistance segregates as expected for a single dominant gene, which we have designated Barley stripe mosaic virus resistance 1 (Bsr1). We constructed a genetic linkage map of the RIL population using SNP markers to map this gene to within 705 Kb of the distal end of the top of chromosome 3. Additional CAPS and Indel markers were used to fine map Bsr1 to a 23 Kb interval containing five putative genes. Our study demonstrates the power of using RILs to rapidly map the genetic determinants of BSMV resistance in Brachypodium. Moreover, the RILs and their associated genetic map, when combined with the complete genomic sequence of Brachypodium, provide new resources for genetic analyses of many other traits. 相似文献
16.
The molecular basis of potassium nutrition in plants 总被引:4,自引:0,他引:4
Christina J. Smart David F. Garvin James P. Prince William J. Lucas Leon V. Kochian 《Plant and Soil》1996,187(1):81-89
Over the last five years, the cloning and characterization of K+ transport genes corresponding to K+ channels (KAT1, AKT1, KST1, AKT2), associated subunits (KAB1) and a high-affinity transporter (HKT1) has opened up important new avenues for research on plant K+ nutrition. With the abundance of molecular data now available it seems timely to link this information with the wealth of data previously accumulated on the physiology of plant K+ acquisition. The ultimate goal of all this research is to gain a better understanding of K+ transport and nutrition in the intact plant. Thus it is important to begin to integrate the molecular research with results from biochemical and physiological research conducted at the cellular, root and whole plant levels. This article will focus on describing the features of the cloned K+ transporters and their possible roles in mediating high- and low-affinity K+ uptake from the soil, as well as how K+ acquisition may be regulated.Abbreviations NEM
N-ethyl maleimide
- PCMBS
p-chloromercuribenzene sulphonic acid 相似文献
17.
18.
Thyrotropin-releasing hormone in the gastrointestinal tract. 总被引:10,自引:0,他引:10
J E Morley T J Garvin A E Pekary J M Hershman 《Biochemical and biophysical research communications》1977,79(1):314-318
TRH immunoreactivity has been shown to occur throughout the rat gastrointestinal tract. This immunoreactivity demonstrates parallelism with TRH, is destroyed by fresh human serum, and co-chromatographs with TRH on a Sephadex G-10 column and on a SP Sephadex C-25 column. In addition pancreatic extracts showed bioactivity in a mouse bioassay for TRH. 相似文献
19.
C Franzblau K Schmid B Faris J Beldekas P Garvin H M Kagan B J Baum 《Biochimica et biophysica acta》1976,427(1):302-314
The influence of alpha1-acid glycoprotein on the formation of fibrous long spacing fibers of collagen has been investigated. It was observed that addition of the glycoprotein to dialyzed collagen solutions caused a significant decrease in the intensity of the circular dichroic spectrum of collagen. This phenomenon, which displays an optimum with respect to glycoprotein, is consistent with previous observations of fibrous long spacing fiber formation. Changes in viscosity of collagen initially dissolved in acetic acid were monitored during dialysis. It was found that a significant increase in viscosity must occur during dialysis of collagen before fibrous long spacing formation could take place. This increase in viscosity can be related directly to removal of acetic acid from the collagen solution. Removal of all sialyl residues from the alpha1-acid glycoprotein with neuraminidase prevents fibrous long spacing formation while removal of up to 35% of the sialyl residues has no effect on the interaction of glycoprotein with collagen. Amino acid composition and radioactivity studies suggest that 45-55% of the insoluble fibrous long spacing fibers is glycoprotein. In contrast to native collagen fibers, reduced fibrous long spacing fibers do not contain histidinohydroxymerodesmosine or hydroxylysinonorleucine. Instead, they contain significant quantities of allysine aldol and epsilon-hydroxynorleucine. 相似文献
20.
Numerous transposed sequences of mitochondrial cytochrome oxidase I-II in aphids of the genus Sitobion (Hemiptera: Aphididae) 总被引:4,自引:1,他引:3
Polymerase chain reaction (PCR) products corresponding to 803 bp of the
cytochrome oxidase subunits I and II region of mitochondrial DNA (mtDNA
COI-II) were deduced to consist of multiple haplotypes in three Sitobion
species. We investigated the molecular basis of these observations. PCR
products were cloned, and six clones from one individual per species were
sequenced. In each individual, one sequence was found commonly, but also
two or three divergent sequences were seen. The divergent sequences were
shown to be nonmitochondrial by sequencing from purified mtDNA and Southern
blotting experiments. All seven nonmitochondrial clones sequenced to
completion were unique. Nonmitochondrial sequences have a high proportion
of unique sites, and very few characters are shared between
nonmitochondrial clones to the exclusion of mtDNA. From these data, we
infer that fragments of mtDNA have been transposed separately (probably
into aphid chromosomes), at a frequency only known to be equalled in
humans. The transposition phenomenon appears to occur infrequently or not
at all in closely related genera and other aphids investigated. Patterns of
nucleotide substitution in mtDNA inferred over a parsimony tree are very
different from those in transposed sequences. Compared with mtDNA,
nonmitochondrial sequences have less codon position bias, more even
exchanges between A, G, C and T, and a higher proportion of nonsynonymous
replacements. Although these data are consistent with the transposed
sequences being under less constraint than mtDNA, changes in the
nonmitochondrial sequences are not random: there remains significant
position bias, and probable excesses of synonymous replacements and of
conservative inferred amino acid replacements. We conclude that a
proportion of the inferred change in the nonmitochondrial sequences
occurred before transposition. We believe that Sitobion aphids (and other
species exhibiting mtDNA transposition) may be important for studying the
molecular evolution of mtDNA and pseudogenes. However, our data highlight
the need to establish the true evolutionary relationships between sequences
in comparative investigations.
相似文献