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71.
H. L. Neibergs A. M. Ryan J. E. Womack R. L. Spooner J. L. Williams 《Animal genetics》1994,25(5):313-317
Polymerase chain reaction (PCR) primers designed to amplify the octapeptide repeat region of the bovine prion gene were used to test the association of genotypes with bovine spongiform encephalitis (BSE) in 56 BSE-affected and 177 unaffected animals. Three alleles (A, B, C) were detected as single-strand conformation polymorphisms (SSCPs) and two alleles (1,2 representing six or five copies of the octapeptide repeat respectively) were detected as amplified double-strand fragment length polymorphisms (AMFLPs). Observed genotypes of SSCPs and AMFLPs were analysed by x-square. The SSCP genotypes of nuclear family members of animals with BSE and BSE-affected animals were different (P < 0.001, P < 0.01) from unrelated animals of the same breed without BSE. No genotypic differences were found between the BSE-affected animals and their relatives (P > 0.469). No AMFLP genotypic differences were detected between BSE-affected animals, their relatives, unrelated animals of the same breed or animals of different breeds (P > 0.05). These data suggest that BSE-affected animals and their relatives are more likely to have the AA SSCP genotype than unrelated animals of the same breed or animals of different breeds. 相似文献
72.
Vascular Development and Sap Flow in Apple Pedicels 总被引:4,自引:2,他引:2
Xylem and phloem tissues of the pedicel of apple fruit increasein cross-sectional area throughout development. The increasein phloem is similar in the two cultivars examined (Cox's OrangePippin and Royal Gala) and reflects a steadily increasing phloemsap flow to the fruit. The increase in xylem tissue is due toa proliferation of non-conducting, structural, components sinceclose examination reveals no increase in the number of vesselelements from just after flowering onwards. The greater number,and the larger diameter, of the vessels in Cox's explains theinitially higher xylem conductance found in this cultivar. In vitro measurements of xylem exudation reveal a decline duringthe growing season in the xylem conductance of both cultivarsand an increasing proportion of fruit (particularly in Cox's)in which the xylem comes to be totally non-conducting. Thisobservation is in line with previously reported measurementsof xylem sap flow in vivo. The straightforward techniques used in this study offer a feasiblealternative to more arduous methods of assessing xylem and phloemsap flows and their balance during growth.Copyright 1994, 1999Academic Press Apple, xylem, phloem, vascular development, sap flow, Malus domestica Borkh 相似文献
73.
The objective of this study was to monitor and compare follicle populations and follicular development in pregnant and nonpregnant sows from Day 3 to Day 20 after breeding. Twenty-four sows were paired within parity on the day of artificial insemination and were randomly allocated within pair for insemination with either killed (n=12) or live spermatozoa (n=12). All the sows were artificially inseminated with the pooled ejaculate of the same boar. From Day 3 through Day 20 post estrus, ovarian follicles were scanned daily by ultrasonography. Ultrasound images were recorded on videotape and were retrospectively analyzed. Follicles were mapped to indentify the existence of follicular waves. The follicles were then classified as small (< 3 mm), medium (3-5 mm), or large (>/=5 mm). Pregnancy diagnosis was performed on Day 21 by ultrasonography. Pregnant sows maintained a constant proportion of the follicle population in the small, medium and large follicle categories. However, in the nonpregnant sows, the proportion of follicles in the various size categories remained constant until Day 15. Thereafter, the proportion of small follicles decreased (P < 0.05) from Day 15 to 20, and the proportions of medium and large follicles increased (P < 0.05). The predictability of pregnancy status on Day 20 based on follicle populations in any of the 3 follicle categories was low. Moreover, there was no evidence of follicular waves during the estrous cycle or early pregnancy. In conclusion, the proportion of small follicles decreased while medium and large follicle increased from Day 15 through Day 20 of the estrous cycle, but not during a similar stage of pregnancy. This latter finding concurs with follicle recruitment from the pool of small follicles for ovulation following PGF2alpha secretion to induce luteolysis, which reduces progesterone concentrations and thereby allows for the stimulation of the pool of small follicles by gonadotropins. 相似文献
74.
Purification of Potato Leaf Plasma Membrane Protein pp34, a Protein Phosphorylated in Response to Oligogalacturonide Signals for Defense and Development 总被引:3,自引:0,他引:3 下载免费PDF全文
A potato (Solanum tuberosum L.) plasma membrane protein called pp34, the only known example of a plasma membrane protein that is phosphorylated specifically in response to defined Oligogalacturonide signals in plants, has been purified to apparent homogeneity. Polyclonal antibodies raised in rabbits against the purified pp34 protein immunoprecipitated a single thiophosphorylated protein species from potato plasma membranes, as analyzed by two-dimensional denaturing electrophoresis and fluorography. The pp34 antibodies also recognized a single protein in tomato (Lycopersicon esculentum L.) membranes that is thiophosphorylated in response to Oligogalacturonide elicitors, as demonstrated by western blotting and specific immunoprecipitation. These experiments confirm the identity of the tomato membrane protein as a pp34 homolog and establish the high monospecificity of the pp34 antibodies. This will permit further investigation of the role of protein phosphorylation in oligouronide signaling for defensive genes in potato and tomato plants. 相似文献
75.
Effects of strength training on bone mineral density: hormonal and bone turnover relationships 总被引:9,自引:0,他引:9
76.
The amino-terminal one-third of pseudorabies virus glycoprotein gIII contains a functional attachment domain, but this domain is not required for the efficient penetration of Vero cells. 总被引:7,自引:6,他引:1 下载免费PDF全文
We have examined the attachment and penetration phenotypes of several glycoprotein gIII mutants of pseudorabies virus (PRV) and have identified the first one-third of gIII as a region that mediates efficient virus attachment to PK15 and Vero cells. This portion of gIII, amino acids 25 through 157 of the wild-type sequence, appeared to support attachment by binding to heparinlike molecules on cell surfaces. Virions containing the first one-third of gIII were sensitive to heparin competition and showed greatly reduced infectivity on cells treated with heparinase. PRV virions lacking the first one-third of the mature glycoprotein exhibited only residual binding to cells if challenged by vigorous washing with phosphate-buffered saline at 2 h postinfection at 4 degrees C. This residual binding was resistant to heparin competition, and strains lacking the first one-third of gIII were able to infect cells treated with heparinase as effectively as untreated cells. When we determined the penetration phenotypes for each strain, we found that gIII-mediated virus attachment was necessary for timely penetration of PK15 cells but remarkably was not required for efficient virus penetration of Vero cells. Moreover, wild-type PRV was actually prohibited from rapid penetration of Vero cells by a gIII-heparan sulfate interaction. Our results indicate that initial virus binding to heparan sulfate via glycoprotein gIII is not required for efficient PRV infection of all cell types and may in fact be detrimental in some instances. 相似文献
77.
Interaction between Aluminum Toxicity and Calcium Uptake at the Root Apex in Near-Isogenic Lines of Wheat (Triticum aestivum L.) Differing in Aluminum Tolerance 总被引:6,自引:4,他引:2 下载免费PDF全文
Aluminum (Al) is toxic to plants at pH < 5.0 and can begin to inhibit root growth within 3 h in solution experiments. The mechanism by which this occurs is unclear. Disruption of calcium (Ca) uptake by Al has long been considered a possible cause of toxicity, and recent work with wheat (Triticum aestivum L. Thell) has demonstrated that Ca uptake at the root apex in an Al-sensitive cultivar (Scout 66) was inhibited more than in a tolerant cultivar (Atlas 66) (J.W. Huang, J.E. Shaff, D.L. Grunes, L.V. Kochian [1992] Plant Physiol 98: 230-237). We investigated this interaction further in wheat by measuring root growth and Ca uptake in three separate pairs of near-isogenic lines within which plants exhibit differential sensitivity to Al. The vibrating calcium-selective microelectrode technique was used to estimate net Ca uptake at the root apex of 6-d-old seedlings. Following the addition of 20 or 50 [mu]M AlCl3, exchange of Ca for Al in the root apoplasm caused a net Ca efflux from the root for up to 10 min. After 40 min of exposure to 50 [mu]M Al, cell wall exchange had ceased, and Ca uptake in the Al-sensitive plants of the near-isogenic lines was inhibited, whereas in the tolerant plants it was either unaffected or stimulated. This provides a general correlation between the inhibition of growth by Al and the reduction in Ca influx and adds some support to the hypothesis that a Ca/Al interaction may be involved in the primary mechanism of Al toxicity in roots. In some treatments, however, Al was able to inhibit root growth significantly without affecting net Ca influx. This suggests that the correlation between inhibition of Ca uptake and the reduction in root growth may not be a mechanistic association. The inhibition of Ca uptake by Al is discussed, and we speculate about possible mechanisms of tolerance. 相似文献
78.
Several mineral rhizotoxicities, including those induced by Al3+, H+, and Na+, can be relieved by elevated Ca2+ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca2+ from transport channels or surface ligands that must be occupied by Ca2+ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al3+, that (i) Ca2+, Mg2+, and Sr2+ are equally ameliorative, (ii) that root elongation does not increase as Ca2+ replaces Mg2+ or Sr2+ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al3+ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca2+ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC3+), in contrast to Al3+, was specifically relieved by Ca2+ at the membrane surface. The rhizotoxicity induced by H+ exhibited a weak specific response to Ca2+ at the membrane surface. We conclude that the Ca2+-displacement hypothesis fails in the case of Al3+ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al3+. However, TEC3+, but not Al3+, may be toxic because it inhibits Ca2+ uptake. The nature of the specific H+-Ca2+ interaction is uncertain.Abbreviations {Al3+ }0
chemical activity of Al3+ at the root-cell membrane surface
- {Al3+ }E
chemical activity of Al3+ in the external rooting medium
- E0
electrical potential at the root-cell membrane surface
- HXM2+
hexamethonium ion
- TEC3+
tris(ethylenediamine)cobaltic ion 相似文献
79.
Aims
Woody plant encroachment is a widespread phenomenon affecting treeless or sparsely treed habitats. We aimed to determine the extent and timing of tree and shrub encroachment into rock barrens of eastern Ontario over the last century, and to assess implications for their ongoing management.Location
Queen's University Biological Station in the Frontenac Arch ecoregion.Methods
We quantified the extent of change in woody vegetation in 290 rock barrens using aerial photography from 1925, 1965, and 2008. Composition and structure of woody plant communities in 10 barrens was subsequently quantified in the field using plot-based sampling. Cores or cross-sections were obtained from individuals >1.5 m height and dendrochronological techniques were used to determine their age and identify temporal patterns of any woody encroachment.Results
Aerial photography indicated that the mean proportion of woody plant cover in barrens increased 22.5% from 1925 to 2008. Dendroecological analysis supported this. Few trees were present prior to 1900 and most established since 1960. Fraxinus americana, Juniperus virginiana, and Juniperus communis were the most common woody species colonizing the barrens. Remnants of large Pinus strobus stumps with extensive charring were found in 90% of the sampled barrens at a mean density of 22.6 stumps ha−1.Conclusions
Rock barrens on the Frontenac Arch have changed substantially over the past century; gradually being colonized by trees and shrubs and losing their distinctly open character. Active management — including prescribed fire and mechanical thinning — may be necessary if there is a desire to maintain these barrens and the rare species they support as components of the region's biodiversity. However, identification of a reference state for restoration is complicated by the fact that the structure and composition of these habitats were undoubtedly altered by European land clearance in the 19th century, and that some of these areas likely existed as pine woodlands before that. 相似文献80.
Chathurika Henpita Rajesh Vyas Chastity L. Healy Tra L. Kieu Aditi U. Gurkar Matthew J. Yousefzadeh Yuxiang Cui Aiping Lu Luise A. Angelini Ryan D. O'Kelly Sara J. McGowan Sanjay Chandrasekhar Rebecca R. Vanderpool Danielle Hennessy-Wack Mark A. Ross Timothy N. Bachman Charles McTiernan Smitha P. S. Pillai Warren Ladiges Mitra Lavasani Johnny Huard Donna Beer-Stolz Claudette M. St. Croix Simon C. Watkins Paul D. Robbins Ana L. Mora Eric E. Kelley Yinsheng Wang Timothy D. O'Connell Laura J. Niedernhofer 《Aging cell》2023,22(4):e13782
Cardiomyopathy is a progressive disease of the myocardium leading to impaired contractility. Genotoxic cancer therapies are known to be potent drivers of cardiomyopathy, whereas causes of spontaneous disease remain unclear. To test the hypothesis that endogenous genotoxic stress contributes to cardiomyopathy, we deleted the DNA repair gene Ercc1 specifically in striated muscle using a floxed allele of Ercc1 and mice expressing Cre under control of the muscle-specific creatinine kinase (Ckmm) promoter or depleted systemically (Ercc1−/D mice). Ckmm-Cre+/−;Ercc1−/fl mice expired suddenly of heart disease by 7 months of age. As young adults, the hearts of Ckmm-Cre+/−;Ercc1−/fl mice were structurally and functionally normal, but by 6-months-of-age, there was significant ventricular dilation, wall thinning, interstitial fibrosis, and systolic dysfunction indicative of dilated cardiomyopathy. Cardiac tissue from the tissue-specific or systemic model showed increased apoptosis and cardiac myocytes from Ckmm-Cre+/-;Ercc1−/fl mice were hypersensitive to genotoxins, resulting in apoptosis. p53 levels and target gene expression, including several antioxidants, were increased in cardiac tissue from Ckmm-Cre+/−;Ercc1−/fl and Ercc1−/D mice. Despite this, cardiac tissue from older mutant mice showed evidence of increased oxidative stress. Genetic or pharmacologic inhibition of p53 attenuated apoptosis and improved disease markers. Similarly, overexpression of mitochondrial-targeted catalase improved disease markers. Together, these data support the conclusion that DNA damage produced endogenously can drive cardiac disease and does so mechanistically via chronic activation of p53 and increased oxidative stress, driving cardiac myocyte apoptosis, dilated cardiomyopathy, and sudden death. 相似文献