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1.
Summary The organization and distribution of microfilaments (MFs) in the preprophase bands (PPBs) of tobacco (Nicotiana tabacum L. var. Maryland Mammoth) root tip cells were studied with high pressure freezing and freeze-substitution methods. MFs were present predominantly as single filaments interspersed among microtubules (MTs) throughout the PPB. Some MFs appeared to be associated with MTs, whereas others were not. This is the first time that MFs have been demonstrated in the PPB at the electron microscope level. 相似文献
2.
Protein kinase C and an endogenous substrate associated with adenohypophyseal secretory granules. 下载免费PDF全文
Secretory granules isolated from anterior pituitary glands were examined for Ca2+/phospholipid-dependent protein kinase (protein kinase C) activity as well as the occurrence of granule-associated substrate proteins. Sheep adenohypophyses were fractionated by differential and sucrose-density-gradient centrifugation to yield a granule fraction enriched for luteinizing-hormone (lutropin)-containing secretory granules. Marker-enzyme analysis showed no detectable cytosolic contamination, although there were small amounts of plasma membranes (2-4%) and lysosomes (4-6%) associated with the preparation. As determined by histone-H1 phosphorylation after DEAE-cellulose DE-52 chromatography, protein kinase C activity with a marked dependence on Ca2+ and lipid (4-fold increase in their presence) was evident in the secretory-granule fraction. Phosphorylation in vitro of the secretory-granule fraction by endogenous and exogenous protein kinase C revealed a protein of Mr 36,000, which by two-dimensional SDS/polyacrylamide-gel electrophoresis showed multiple sites of phosphorylation. The Mr-36,000 protein was not found in cytosolic or plasma-membrane fractions and was not phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase. Several secretory-granule proteins served as substrates for the catalytic subunit, the most prominent of which were of Mr 63,000, 23,000 and 21,000. From these data, we suggest that phosphorylation of secretory-granule-associated proteins by protein kinase C and by cyclic AMP-dependent protein kinase may be important in secretion regulation in the anterior pituitary gland. 相似文献
3.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
4.
Infection in Mouse Peritoneal Cavity with a Pyrimidine-requiring Mutant and Naturally Occurring Staphylococcus aureus Strains 总被引:1,自引:0,他引:1
The lethal activity of a thymineless mutant of Staphylococcus aureus Wood 46 strain has been compared with that of three naturally occurring strains: parent Wood 46, Smith, and coagulase-negative SA-13. The thymineless mutant and the parent Wood 46 strain showed a sharp decline in culturable units from the peritoneal cavity in the first 4 hr after their injection. After 6 hr, that is, 2 hr before the mice began to die, the number of culturable units of the thymineless mutant was still declining, whereas that of the parent strain increased; for both strains, the number of units was still lower than that of the inoculum. Although the thymineless mutant, unlike the parent strain, was apparently unable to multiply in mouse peritoneal cavity, it killed mice at a similar rate. The highly virulent Smith strain known to multiply rapidly and the avirulent coagulase-negative SA-13 strain were used as additional controls. Under our experimental conditions, death of mice after the injection of the thymineless mutant in the peritoneal cavity did not seem to be due to bacterial multiplication but to toxicity, death being delayed by antitoxin. The pyrimidine-requiring auxotroph we used could be better material than killed bacteria to study some aspects of the lethal activity of S. aureus. 相似文献
5.
Julie Turgeon Paul D. N. Hebert 《Evolution; international journal of organic evolution》1994,48(6):1855-1865
Freshwater ostracodes show both an exceptionally high incidence of transitions to unisexuality and, in some cases, an extraordinary level of clonal diversity. There is no understanding of the agents promoting these transitions to thelytoky, although it has been suggested that their frequency may set the stage for sexual taxa to infuse clonal diversity into unisexuals. This study examines the nature and origins of clonal diversity in the unisexual ostracode Cyprinotus incongruens. A combination of allozyme and cytogenetic studies revealed the presence of two diploid clones of this species at three temperate sites and ten clones at one arctic site including three diploids, five triploids, and two tetraploids. The low heterozygosity (0%–20%) of its diploid clones suggests that parthenogenesis has arisen spontaneously in C. incongruens rather than through hybridization, as in vertebrate asexuals. Polyploid clones appear to owe their origin to genome additions from sexual taxa, although subsequent mutational divergence has played a role in further enhancing diversity. Two triploid clones have apparently originated from the incorporation of a haploid genome from the sexually reproducing C. glaucus, as evidenced by their high heterozygosity and possession of alleles otherwise found only in that species. Other polyploid clones have likely arisen as a result of interbreeding between bisexual and unisexual C. incongruens. These results suggest that both the incidence of spontaneous transitions to clonality and the frequency of interbreeding with relatives may be the key processes that govern clonal diversity in unisexual ostracodes. 相似文献
6.
The intermediary cell: Minor-vein anatomy and raffinose oligosaccharide synthesis in the Scrophulariaceae 总被引:7,自引:0,他引:7
Minor-vein anatomy, sugar content, sugar synthesis, and translocation were studied in mature leaves of nine members of the Scrophulariaceae to determine if there is a correlation between companion-cell type and class of sugar translocated. Three types of companion cell were found: intermediary cells with extensive plasmodesmatal connections to the bundle sheath; transfer cells with wall ingrowths and few plasmodesmata; and ordinary companion cells with few plasmodesmata and no wall ingrowths. Alonsoa warscewiczii Regal., Verbascum chaixi Vill., and Mimulus cardinalis Dougl. ex. Benth. have intermediary cells and ordinary companion cells in the minor veins. These plants synthesize large amounts of raffinose and stachyose as well as sucrose. Nemesia strumosa Benth., and Rhodochiton atrosanguineum Zucc. have both intermediary cells and transfer cells and make proportionately less raffinose oligosaccharide than the species above. In N. strumosa, a single sieve element may abut both an intermediary cell and a transfer cell. The minor veins of Asarina scandens (Cav.) Penn. have transfer cells and what appear to be modified intermediary cells that have fewer plasmodesmata than other species, and occasional wall ingrowths. Asarina scandens synthesizes little raffinose or stachyose. Cymbalaria muralis P. Gaertn et al. and Linaria maroccana Hook.f. have only transfer cells and Digitalis grandiflora Mill. has only ordinary companion cells; these species make a trace of galactinol and raffinose, but no stachyose. Translocation experiments indicate that there is long-distance movement of raffinose oligosaccharide in these plants, even when it is synthesized in very small quantities in the leaves. We conclude that intermediary cells are as distinct a cell type as the transfer cell. In contrast to transfer cells, which are specialized for uptake of solute from the apoplast, intermediary cells are specialized for symplastic transfer of photoassimilate from the mesophyll and for synthesis of raffinose oligosaccharide. This supports our contention that raffinose oligosaccharide synthesis and symplastic phloem loading are mechanistically linked (Turgeon and Gowan 1990, Plant Physiol. 94, 1244–1249). Minor-vein anatomy and sugar synthesis may be useful characters in determining the phylogenetic relationships of plants in this family.We thank Andrea Wolfe and Wayne Elisens for helpful discussions on the taxonomy of the Scrophulariaceae. This research was supported by National Science Foundation grant DCB-9104159, U.S. Department of Agriculture Competetive Grant 92-37306-7819, and Hatch funds. 相似文献
7.
Cytokinesis, cell expansion, and the potential for cytokinin-autonomous growth in tobacco pith 下载免费PDF全文
Turgeon R 《Plant physiology》1982,70(4):1071-1074
Pith tissue from Nicotiana tabacum L. cv `Maryland Mammoth' or `Wisconsin 38' was isolated, free of vascular tissue, and cultured on a medium containing auxin but no cytokinin. Explants from the apical 1 cm of stem, within the pith rib meristem, initiated callus growth with 100% efficiency. Macroscopically visible callus was evident 5 days after the tissue was isolated, and the cultures grew persistently in the absence of cytokinin. Heat treatment, sometimes used to initiate cytokinin habituation, was not required. Explants from tissue basipetal to the pith rib meristem declined in the frequency of habituation with increasing distance from the shoot apex. Although pith tissue which was growing, in vivo, was more prone than mature tissue to establish cytokinin-habituated callus, the basipetal decline in habituation frequency extended well beyond the zone of cell expansion. Explants from mature pith 40 centimeters or more from the shoot apex grew in the absence of cytokinin with 18% frequency, although the response required at least 2 weeks of culture. Further analysis demonstrated that tissue near the periphery of mature pith was more prone to cytokinin-habituation than tissue from the pith center. 相似文献
8.
Quantitative Analysis of Photosynthate Unloading in Developing Seeds of Phaseolus vulgaris L. : I. The Use of Steady-State Labeling 下载免费PDF全文
The pathway and kinetics of photosynthate unloading in developing seeds of bean (Phaseolus vulgaris L.) were investigated using steady-state labeling with 14CO2. The continuous assimilation of 14CO2 at constant specific activity produced stable tracer fluxes that facilitated straightforward analyses of photosynthate import and unloading in developing seeds. The kinetics of tracer equilibration within intact seeds were compatible with a symplastic route of photosynthate unloading in the seed coat. The import and partitioning of tracer within seeds were partially disrupted by the surgical excision of the distal halves of seeds as practiced during the preparation of “empty” seed coats for perfusion. 相似文献
9.
A Meisels M Roy M Fortier C Morin M Casas-Cordero K V Shah H Turgeon 《Acta cytologica》1981,25(1):7-16
We report on 162 cases of human papillomavirus (HPV) infection of the cervix seen in a two-year period in which the cell sample showed such marked atypia that errors of interpretation could easily have been made. These atypical condylomata are difficult to diagnose cytologically as well as histologically because they mimic dysplasia or carcinoma in situ and, on smears, even invasive squamous carcinoma. HPV particles associated with fibrillar material were found within nuclei of these lesions; their nature was further proved by the immunoperoxidase test. This new form of HPV infection of the cervix showed a 9.1% rate of progression to more advanced cervical lesions. The cytologic finding of atypical condylomata is an indication for colposcopy, confirmative biopsy and appropriate treatment. 相似文献
10.
Qiu Y Patwa TH Xu L Shedden K Misek DE Tuck M Jin G Ruffin MT Turgeon DK Synal S Bresalier R Marcon N Brenner DE Lubman DM 《Journal of proteome research》2008,7(4):1693-1703
Colorectal cancer (CRC) remains a major worldwide cause of cancer-related morbidity and mortality largely due to the insidious onset of the disease. The current clinical procedures utilized for disease diagnosis are invasive, unpleasant, and inconvenient; hence, the need for simple blood tests that could be used for the early detection of CRC. In this work, we have developed methods for glycoproteomics analysis to identify plasma markers with utility to assist in the detection of colorectal cancer (CRC). Following immunodepletion of the most abundant plasma proteins, the plasma N -linked glycoproteins were enriched using lectin affinity chromatography and subsequently further separated by nonporous silica reversed-phase (NPS-RP)-HPLC. Individual RP-HPLC fractions were printed on nitrocellulose coated slides which were then probed with lectins to determine glycan patterns in plasma samples from 9 normal, 5 adenoma, and 6 colorectal cancer patients. Statistical tools, including principal component analysis, hierarchical clustering, and Z-statistics analysis, were employed to identify distinctive glycosylation patterns. Patients diagnosed with colorectal cancer or adenomas were shown to have dramatically higher levels of sialylation and fucosylation as compared to normal controls. Plasma glycoproteins with aberrant glycosylation were identified by nano-LC-MS/MS, while a lectin blotting methodology was used to validate proteins with significantly altered glycosylation as a function of cancer progression. The potential markers identified in this study for diagnosis to distinguish colorectal cancer from adenoma and normal include elevated sialylation and fucosylation in complement C3, histidine-rich glycoprotein, and kininogen-1. These potential markers of colorectal cancer were subsequently validated by lectin blotting in an independent set of plasma samples obtained from 10 CRC patients, 10 patients with adenomas, and 10 normal subjects. These results demonstrate the utility of this strategy for the identification of N -linked glycan patterns as potential markers of CRC in human plasma, and may have the utility to distinguish different disease states. 相似文献