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151.
Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency. 总被引:3,自引:1,他引:2 下载免费PDF全文
F. X. Arredondo-Vega I. Santisteban S. Kelly C. M. Schlossman D. T. Umetsu M. S. Hershfield 《American journal of human genetics》1994,54(5):820-830
Adenosine deaminase (ADA) deficiency usually causes severe combined immune deficiency in infancy. Milder phenotypes, with delayed or late onset and gradual decline in immune function, also occur and are associated with less severely impaired deoxyadenosine (dAdo) catabolism. We have characterized the mutations responsible for ADA deficiency in siblings with striking disparity in clinical phenotype. Erythrocyte dAdo nucleotide pool size, which reflects total residual ADA activity, was lower in the older, more mildly affected sib (RG) than in her younger, more severely affected sister (EG). Cultured T cells, fibroblasts, and B lymphoblasts of RG had detectable residual ADA activity, while cells of EG did not. ADA mRNA was undetectable by northern analysis in these cells of both patients. Both sibs were found to be compound heterozygotes for the following novel splicing defects: (1) a G+1-->A substitution at the 5' splice site of IVS 2 and (2) a complex 17-bp rearrangement of the 3' splice site of IVS 8, which inserted a run of seven purines into the polypyrimidine tract and altered the reading frame of exon 9. PCR-amplified ADA cDNA clones with premature translation stop codons arising from aberrant pre-mRNA splicing were identified, which were consistent with these mutations. However, some cDNA clones from T cells of both patients and from fibroblasts and Epstein-Barr virus (EBV)-transformed B cells of RG, were normally spliced at both the exon 2/3 and exon 8/9 junctions. A normal coding sequence was documented for clones from both sibs. The normal cDNA clones did not appear to arise from either contamination or PCR artifact, and mosaicism seems unlikely to have been involved. These findings suggest (1) that a low level of normal pre-mRNA splicing may occur despite mutation of the invariant first nucleotide of the 5' splice donor sequence and (2) that differences in efficiency of such splicing may account for the difference in residual ADA activity, immune dysfunction, and clinical severity in these siblings. 相似文献
152.
Membrane potential and ionic currents were studied in cultured rabbit retinal pigment epithelial (RPE) cells using whole-cell patch clamp and perforated-patch recording techniques. RPE cells exhibited both outward and inward voltage-dependent currents and had a mean membrane capacitance of 26±12 pF (sd, n=92). The resting membrane potential averaged ?31±15 mV (n=37), but it was as high as ?60 mV in some cells. When K+ was the principal cation in the recording electrode, depolarization-activated outward currents were apparent in 91% of cells studied. Tail current analysis revealed that the outward currents were primarily K+ selective. The most frequently observed outward K+ current was a voltage- and time-dependent outward current (I K) which resembled the delayed rectifier K+ current described in other cells. I K was blocked by tetraethylammonium ions (TEA) and barium (Ba2+) and reduced by 4-aminopyridine (4-AP). In a few cells (3–4%), depolarization to ?50 mV or more negative potentials evoked an outwardly rectifying K+ current (I Kt) which showed more rapid inactivation at depolarized potentials. Inwardly rectifying K+ current (I KI) was also present in 41% of cells. I KI was blocked by extracellular Ba2+ or Cs+ and exhibited time-dependent decay, due to Na+ blockade, at negative potentials. We conclude that cultured rabbit RPE cells exhibit at least three voltage-dependent K+ currents. The K+ conductances reported here may provide conductive pathways important in maintaining ion and fluid homeostasis in the subretinal space. 相似文献
153.
154.
Carbon dioxide consumption during soil development 总被引:5,自引:1,他引:4
Oliver A. Chadwick Eugene F. Kelly Dorothy M. Merritts Ronald G. Amundson 《Biogeochemistry》1994,24(3):115-127
Carbon is sequestered in soils by accumulation of recalcitrant organic matter and by bicarbonate weathering of silicate minerals. Carbon fixation by ecosystems helps drive weathering processes in soils and that in turn diverts carbon from annual photosynthesis-soil respiration cycling into the long-term geological carbon cycle. To quantify rates of carbon transfer during soil development in moist temperate grassland and desert scrubland ecosystems, we measured organic and inorganic residues derived from the interaction of soil biota and silicate mineral weathering for twenty-two soil profiles in arkosic sediments of differing ages. In moist temperate grasslands, net annual removal of carbon from the atmosphere by organic carbon accumulation and silicate weathering ranges from about 8.5 g m–2 yr–1 for young soils to 0.7 g M–2 yr–1 for old soils. In desert scrublands, net annual carbon removal is about 0.2 g m–2 yr–1 for young soils and 0.01 g m–2 yr–1 for old soils. In soils of both ecosystems, organic carbon accumulation exceeds CO2 removal by weathering, however, as soils age, rates of CO2 consumption by weathering accounts for greater amounts of carbon sequestration, increasing from 2% to 8% in the grassland soils and from 2% to 40% in the scrubland soils. In soils of desert scrublands, carbonate accumulation far outstrips organic carbon accumulation, but about 90% of this mass is derived from aerosolic sources that do not contribute to long-term sequestration of atmospheric carbon dioxide. 相似文献
155.
Gang Fang K. Venkateswarlu Diane E. Kelly Steven L. Kelly 《Biotechnology letters》1994,16(12):1253-1258
The Saccharomyces cerevisiae strain AH22 was capable of human P4501A1 expression without detectable background of yeast P450, unlike ATCC44773. Repeated backcrossing to AH22 produced a strain allowing transformation by vectors carrying various common selectable markers. Background yeast xenobiotic metabolism was observed only with growth on complex medium. 相似文献
156.
Dandan Sun Douglas Kintner James H. Fitzpatrick Sherrie E. Emoto Pierre G. Braquet Nicolas G. Bazan David D. Gilboe 《Neurochemical research》1994,19(4):525-528
The effects of the platelet-activating factor antagonist BN 50739 and a free radical scavenger dimethyl sulfoxide on the accumulation of free fatty acids in post-ischemic canine brain are reported. Following 14 min of complete normothermic ischemia and 60 min of reperfusion, the total brain FFAs were approximately 150% higher than in the control group (p<0.05). Perfusion with the platelet-activating factor antagonist BN50739 in its diluent dimethyl sulfoxide during 60 min of post-ischemic reoxygenation resulted in a 61.8% (p<0.01) reduction in the total brain free fatty acid accumulation. Palmitic, stearic, oleic, linoleic, and arachidonic acids decreased by 53.8%, 63.5%, 69.0%, 47.4%, and 57.2%, respectively. Although dimethyl sulfoxide alone caused stearic and arachidonic acids to return to the normal concentration range, BN 50739 had a significant influence on recovery of palmitic, oleic, and linoleic acids and was previously shown to provide significant therapeutic protection against damage to brain mitochondria following an ischemic episode. Because free fatty acid accumulation is one of the early phenomena in cerebral ischemia, this study provides evidence to support the hypothesis that both platelet-activating factor and free radicals are involved in initiating cerebral ischemic injury. 相似文献
157.
Relationship between osmoprotection and the structure and intracellular accumulation of betaines by Escherichia coli 总被引:2,自引:0,他引:2
Barbara A. Peddie Michael Lever Colin M. Hayman Kelly Randall Stephen T. Chambers 《FEMS microbiology letters》1994,120(1-2):125-131
Abstract Naturally occuring betaines, especially glycine betaine and proline betaine, were accumulated by Escherichia coli from urine. In synthetic hyperosmotic medium, with an homologous series of added betaines, (CH3 )3 N+ -(CH2 ) n -COO− , osmoprotective activity and intracellular accumulation decreased monotonically as n increased from 1 to 5. In contrast, α -substituted glycine betaines were accumulated in a similar manner to glycine betaine, but with different osmoprotective activities. Arsenobetaine, with a quaternary arsonium group, was also accumulated but amino acids which can become negatively charged in a chemically basic environment were not. 相似文献
158.
J. Boultwood C. Fidler S. Lewis S. Kelly H. Sheridan T. J. Littlewood V. J. Buckle J. S. Wainscoat 《Genomics》1994,19(3)
Molecular mapping techniques have defined the region of gene loss in two patients with the 5q- syndrome and uncharacteristically small 5q deletions (5q31-q33). The allelic loss of 10 genes localized to 5q23-qter (centromere-CSF2-EGR1-FGFA-GRL-ADRB2-CSF1R-SPARC-GLUH1-NKSF1-FLT4-telomere) was investigated in peripheral blood cell fractions. Gene dosage experiments demonstrated that CSF2, EGR1, NKSF1, and FLT4 were retained on the 5q- chromosome in both patients and that FGFA was retained in one patient, thus placing these genes outside the critical region. GRL, ADRB2, CSF1R, SPARC, and GLUH1 were shown to be deleted in both patients. The proximal breakpoint is localized between EGR1 and FGFA in one patient and between FGFA and ADRB2 in the other, and the distal breakpoint is localized between GLUH1 and NKSF1 in both patients. Pulsed-field gel electrophoresis was used to map the 5q deletion breakpoints, and breakpoint-specific fragments were detected with FGFA in the granulocyte but not the lymphocyte fraction of one patient. This study has established the critical region of gene loss of the 5q- chromosome in the 5q- syndrome, giving the location for a putative tumor-suppressor gene in the 5.6-Mb region between FGFA and NKSF1. 相似文献
159.
Three protocols for the determination of inorganic and organic sulfur fractions were tested for their suitability to estimate total indigenous organic sulfur (Sorg) and35Sorg formed from added35SO4
2– in sediments of chemically dilute lakes in the ELA. The protocols tested have all been reported in the literature. It was found that two protocols involving sequential analyses for S fractions following acid treatment gave estimates of both Sorg and35Sorg up to 87% lower than a non-sequential protocol. The low estimates were largely due to hydrolysis and solubilization of solid phase S which was then removed in a rinsing step. The non-sequential protocol, in which total reduced inorganic sulfur and total sulfur were determined on separate aliquots, is recommended as the most reliable of the three. Individual analyses in this protocol were verified for these lake sediments using a variety of S standards. 相似文献
160.
Identification of RAPD markers linked to a major rust resistance gene block in common bean 总被引:6,自引:0,他引:6
S. D. Haley P. N. Miklas J. R. Stavely J. Byrum J. D. Kelly 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,86(4):505-512
Rust in bean (Phaseolus vulgaris L.), caused byUromyces appendiculatus (Pers.) Unger var.appendiculatus [ =U. phaseoli (Reben) Wint.], is a major disease problem and production constraint in many parts of the world. The predominant form of genetic control of the pathogen is a series of major genes which necessitate the development of efficient selection strategies. Our objective was focused on the identification of RAPD (random amplified polymorphic DNA) markers linked to a major bean rust resistance gene block enabling marker-based selection and facilitating resistance gene pyramiding into susceptible bean germplasm. Using pooled DNA samples of genotyped individuals from two segregating populations, we identified two RAPD markers linked to the gene block of interest. One such RAPD, OF10970 (generated by a 5-GGAAGCTTGG-3 decamer), was found to be closely linked (2.15±1.50 centi Morgans) in coupling with the resistance gene block. The other identified RAPD, OI19460 (generated by a 5-AATGCGGGAG-3 decamer), was shown to be more tightly linked (also in coupling) than OF10970 as no recombinants were detected among 97 BC6F2 segregating individuals in the mapping population. Analysis of a collection of resistant and susceptible cultivars and experimental lines, of both Mesoamerican and Andean origin, revealed that: (1) recombination between OF10970 and the gene block has occurred as evidenced by the presence of the DNA fragment in several susceptible genotypes, (2) recombination between OI19460 and the gene block has also occurred indicating that the marker is not located within the gene block itself, and (3) marker-facilitated selection using these RAPD markers, and another previously identified, will enable gene pyramiding in Andean germplasm and certain Mesoamerican bean races in which the resistance gene block does not traditionally exist. Observations of variable recombination among Mesoamerican bean races suggested suppression of recombination between introgressed segments and divergent recurrent backgrounds.Research supported by the Michigan Agricultural Research Station and the USDA-ARS. Mention of a trademark or a proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable 相似文献