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71.
Phillip W. Berman Gerald R. Nakamura Lavon Riddle Henry Chiu Karen Fisher Mark Champe Alane M. Gray Pamela Ward Sherman Fong 《Journal of cellular biochemistry》1993,52(2):183-195
Full-length (membrane bound) and truncated (secreted) forms of the beta 2 integrin heterodimer, CD11b/CD18 (Mac-1), were expressed in a human kidney cell line (293) that normally does not express leukocyte adhesion molecules (Leu-CAMs). The biosynthesis of recombinant Mac-1 in 293 cells differed from that reported for leukocytes in that heterodimer formation was not required for CD11b to be exported to the cell surface. A stable cell line was constructed that constitutively secreted the recombinant, truncated Mac-1 heterodimer into growth conditioned cell culture medium. A novel monoclonal antibody that enabled an immunoaffinity method for the selective purification of recombinant Mac-1 heterodimers was identified. Sufficient protein was purified to allow the first measurement of the 50% inhibitory concentration (IC50) for CD11b/CD18 and for the direct comparison of the inhibitory activity of recombinant soluble Mac-1 with that of various CD18 and CD11b specific monoclonal antibodies. Purified recombinant soluble Mac-1 inhibited the binding of neutrophils, activated by opsonized zymosan or fMet-Leu-Phe peptide, to human umbilical vein endothelial cells. Similarly, the recombinant integrin was effective in inhibiting the binding of unactivated neutrophils to tumor necrosis factor (TNF-alpha) activated endothelial cells. The availability of an abundant source of purified, biologically active Mac-1 will enable direct physical and chemical investigations into the relationship between the structure and function of this leukocyte adhesion molecule. 相似文献
72.
Pamela O'Neil 《American journal of botany》1992,79(9):1024-1030
The purpose of this study was to assess variation in male and female reproductive success among the three morphs of the tristylous plant, Lythrum salicaria. Fluorescent dyes were used as pollen analogs to determine whether morphs differ in their abilities to donate and receive pollen, and actual and potential seed set was measured with a hand pollination experiment. Dye transfer among morphs was highly asymmetric, with more frequent transfer from the short-styled morph to the long- and mid-styled morphs. This suggests that shorts are performing better at pollen donation and longs and mids are performing better at pollen receipt. All flowers on 95 plants were hand pollinated to test whether female reproductive success is more pollen-limited in the short-styled morph than in other morphs. Hand-pollinated short-styled plants had significantly higher total seed mass and more seeds per capsule than short controls, whereas hand pollination failed to increase seed set in long and mid morphs. As predicted, short-styled morphs showed significant pollen limitation, whereas seed set in long- and midstyled morphs was not pollen-limited. Thus, in Lythrum salicaria asymmetrical pollen flow generates morph-specific differences in male and female fitness. 相似文献
73.
Christian Brochmann Pamela S. Soltis Douglas E. Soltis 《American journal of botany》1992,79(6):673-688
Draba (Brassicaceae) is well known for its taxonomic complexity in arctic and alpine floras, and the polyploids in particular present vexing taxonomic problems. It has been suggested that polyploids in Draba may have formed recurrently from different populations of the parental species (polytopy), and it is also possible that a given taxonomic species may actually comprise several polyploid races, each originating from different progenitor species (polyphyly). To unravel the taxonomic complexity of polyploid Draba in the Nordic area, we investigated three of the most morphologically variable species and their possible progenitors using enzyme electrophoresis and restriction site analysis of chloroplast DNA (cpDNA) and nuclear ribosomal RNA genes (rDNA): D. norvegica (6x), D. lactea (6x), and D. corymbosa (16x). Electrophoretic analyses of progeny showed high levels of fixed heterozygosity in all three polyploids, demonstrating that all are genetic alloploids. Electrophoretic and rDNA data indicate that polytopic and/or polyphyletic origins have contributed to the complexity of these polyploids. However, a lack of cpDNA variation among the species limited the usefulness of this molecule for analysis of polyploid origins. The considerable electrophoretic variation observed in D. norvegica necessitates a minimum of three and probably 13 independent origins. Electrophoretic and rDNA data suggest that D. lactea and D. corymbosa are polyphyletic polyploids. Crossing data also support that D. corymbosa is polyphyletic. Given the widespread geographic distributions of these species and their possible progenitors, and that the populations analyzed represent only a small fraction of their geographic distributions, it is likely that these species have formed numerous times in different areas. As more molecular analyses of polyploids are completed, the data continue to suggest that multiple origins of polyploids are the rule rather than the exception. 相似文献
74.
Douglas E. Soltis Pamela S. Soltis 《Evolution; international journal of organic evolution》1989,43(3):586-594
Although there is an extensive literature on the genetic attributes of allopolyploids, very little information is available regarding the genetic consequences of autopolyploidy in natural populations. We therefore addressed the major predicted genetic consequences of autopolyploidy using diploid and tetraploid populations of Tolmiea menziesii. Individual autotetraploid plants frequently maintain three or four alleles at single loci: 39% of the 678 tetraploid plants exhibited three or four alleles for at least one locus. Heterozygosity was also significantly higher in autotetraploid populations than in diploid populations: H° = 0.070 and 0.237 in diploid and tetraploid Tolmiea, respectively. Most of the genetic diversity in T. menziesii is maintained within populations (ratio of gene diversity within populations to mean total genetic diversity = 0.636). The total genetic diversity due to differentiation between the two cytotypes is only 0.055. Such a low degree of differentiation between cytotypes would be expected between a diploid and its autotetraploid derivative. Most diploid and all tetraploid populations examined are in genetic equilibrium. Diploid and tetraploid Tolmiea share three or four alleles at six of eight polymorphic loci. This suggests that either autotetraploid Tolmiea was formed via crossing of genetically different diploids (perhaps via a triploid intermediate) or autopolyploidy occurred more than once in separate individual plants, followed by later crossing of autotetraploids. 相似文献
75.
Riccardo Pellegrino Raffaele Dellaca Peter T Macklem Andrea Aliverti Stefania Bertini Pamela Lotti PierGiuseppe Agostoni Alessandro Locatelli Vito Brusasco 《Journal of applied physiology》2003,95(2):728-734
Lung mechanics and airway responsiveness to methacholine (MCh) were studied in seven volunteers before and after a 20-min intravenous infusion of saline. Data were compared with those of a time point-matched control study. The following parameters were measured: 1-s forced expiratory volume, forced vital capacity, flows at 40% of control forced vital capacity on maximal (Vm(40)) and partial (Vp(40)) forced expiratory maneuvers, lung volumes, lung elastic recoil, lung resistance (Rl), dynamic elastance (Edyn), and within-breath resistance of respiratory system (Rrs). Rl and Edyn were measured during tidal breathing before and for 2 min after a deep inhalation and also at different lung volumes above and below functional residual capacity. Rrs was measured at functional residual capacity and at total lung capacity. Before MCh, saline infusion caused significant decrements of forced expiratory volume in 1 s, Vm(40), and Vp(40), but insignificantly affected lung volumes, elastic recoil, Rl, Edyn, and Rrs at any lung volume. Furthermore, saline infusion was associated with an increased response to MCh, which was not associated with significant changes in the ratio of Vm(40) to Vp(40). In conclusion, mild airflow obstruction and enhanced airway responsiveness were observed after saline, but this was not apparently due to altered elastic properties of the lung or inability of the airways to dilate with deep inhalation. It is speculated that it was likely the result of airway wall edema encroaching on the bronchial lumen. 相似文献
76.
77.
Detached leaves of Bryophyllum fedtschenkoi Hamet et Perrier kept in normal air show a single period of net CO2 fixation on transfer to constant darkness at temperatures in the range 0–25 °C. The duration of this initial fixation period is largely independent of temperature in the range 5–20 °C, but lengthens very markedly at temperatures below 4 °C, and is reduced at temperatures above 25 °C. The onset of net fixation of CO2 on transfer of leaves to constant darkness is immediate at low temperatures, but is delayed as the temperature is increased. The ambient temperature also determines whether or not a circadian rhythm of CO2 exchange occurs. The rhythm begins to appear at about 20 °C, is most evident at 30 °C and becomes less distinct at 35 °C. The occurrence of a distinct circadian rhythm in CO2 output at 30° C in the absence of a detectable rhythm in PEPCase kinase activity shows that the kinase rhythm is not a mandatory requirement for the rhythm of PEPCase activity. However, when it occurs, the kinase rhythm undoubtedly amplifies the PEPCase rhythm.Abbreviation PEPCase
phosphoenolpyruvate carboxylase
We thank the Agricultural and Food Research Council for financial support for this work. 相似文献
78.
Zfy1 is a mouse Y chromosomal gene encoding a zincfinger protein which is thought to have some function during spermatogenesis. Here we show that, when introduced into tissue culture cells, Zfy1 is targeted to the nucleus. Two independent signals are present within the protein for nuclear localization. This nuclear Zfy1 protein is able to bind strongly to DNA-cellulose and, using site-selection assays, we have identified specific Zfy1 DNA binding sites. Taken together these results suggest that Zfy1 is a nuclear-located sequence-specific DNA binding protein which functions during spermatogenesis. 相似文献
79.
Joan E. Kuster Mary H. Guarnieri Jeffrey G. Ault Lorraine Flaherty Pamela J. Swiatek 《Mammalian genome》1997,8(9):673-681
The laminin-5 molecule functions in the attachment of various epithelia to basement membranes. Mutations in the laminin-5-coding
genes have been associated with Herlitz junctional epidermolysis bullosa (HJEB), a severe and often lethal blistering disease
of humans. Here we report the characterization of a spontaneous mouse mutant with an autosomal recessive blistering disease.
These mice exhibit sub-epithelial blisters of the skin and mucosal surfaces and abnormal hemidesmosomes lacking sub-basal
dense plates. By linkage analysis the genetic defect was localized to a 2-cM region on distal Chromosome (Chr) 1 where a laminin-5
subunit gene, LamB3, was previously localized. LamB3 mRNA and laminin-5 protein were undetectable by Northern blot analysis and immunohistochemical methods, respectively. DNA
sequence analysis indicated that the LamB3 genetic defect resulted from disruption of the coding sequence by insertion of an intracisternal-A particle (IAP) at an exon/intron
junction. These findings suggest a role for laminin-5 in hemidesmosome formation and indicate that the LamB3
IAP
mutant is a useful mouse model for HJEB.
Received: 27 March 1997 / Accepted: 14 May 1997 相似文献
80.
Inhibition of endoplasmic reticulum-to-Golgi traffic by poliovirus protein 3A: genetic and ultrastructural analysis. 总被引:9,自引:8,他引:1 下载免费PDF全文
Poliovirus protein 3A, only 87 amino acids in length, is a potent inhibitor of protein secretion in mammalian cells, blocking anterograde protein traffic from the endoplasmic reticulum (ER) to the Golgi complex. The function of viral protein 3A in blocking protein secretion is extremely sensitive to mutations near the N terminus of the protein. Deletion of the first 10 amino acids or insertion of a single amino acid between amino acids 15 and 16, a mutation that causes a cold-sensitive defect in poliovirus RNA replication, abrogates the inhibition of protein secretion although wild-type amounts of the mutant proteins are expressed. Immunofluorescence light microscopy and immunoelectron microscopy demonstrate that 3A protein, expressed in the absence of other viral proteins, colocalizes with membranes derived from the ER. The precise topology of 3A with respect to ER membranes is not known, but it is likely to be associated with the cytosolic surface of the ER. Although the glycosylation of 3A in translation extracts has been reported, we show that tunicamycin, under conditions in which glycosylation of cellular proteins is inhibited, has no effect on poliovirus growth. Therefore, glycosylation of 3A plays no functional role in the viral replicative cycle. Electron microscopy reveals that the ER dilates dramatically in the presence of 3A protein. The absence of accumulated vesicles and the swelling of the ER-derived membranes argues that ER-to-Golgi traffic is inhibited at the step of vesicle formation or budding from the ER. 相似文献