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1.
The binding of norepinephrine (NE) to plasma proteins of fresh human blood obtained from healthy volunteers was studied by ultrafiltration at different NE concentrations and incubation times at 37 degrees C. At 1.7 nM L-[3H]-NE binding was approximately 25%. The binding was rapid and was not influenced by the incubation time. [3H]-NE could be dissociated from its binding sites by acid precipitation and, after HPLC, showed to be unchanged NE. No difference in NE binding was found between plasma collected in EGTA-GSH or heparin solution. There was no degradation of NE when incubated in plasma at 37 degrees C for 10 h, even without the addition of antioxidants. Therefore, in the present study, binding represented interaction of unchanged NE with plasma proteins. The whole plasma binding was saturable over the range of 0.66 nM to 0.59 mM of NE. Scatchard plot of specific binding revealed high-affinity sites with a Kd of 5.4 nM and a Bmax of 3.9 fmoles.mg-1 protein, and low-affinity sites with a Kd of 2.7 microM and a Bmax of 3.3 pmoles.mg-1 protein. Electrophoretic characterization of NE-binding proteins showed that about 60% of bound NE was associated to albumin, and 20% to prealbumin. NE binding to pure human plasma proteins was also studied using ultrafiltration. Scatchard analyses revealed a single class of very high-affinity binding sites for prealbumin (Kd 4.9 nM), a single class of binding sites for alpha 1-acid glycoprotein (Kd 54 microM) and two classes of binding sites for albumin with high (Kd 1.7 microM) and low (Kd 0.8 mM) affinities respectively. The main results obtained in this study - a) reversibility of NE binding, b) stability of free and bound NE in plasma, c) involvement of the prealbumin as a specific binding protein - point out to a specific transport for NE in human blood plasma.  相似文献   
2.
The alpha-like globin gene cluster in rabbits contains embryonic zeta- globin genes, an adult alpha-globin gene, and theta-globin genes of undetermined function. The basic arrangement of genes, deduced from analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3'. However, the pattern of restriction fragments containing zeta- and theta-globin genes varies among individual rabbits. Analysis of BamHI fragments of genomic DNA from 24 New Zealand white rabbits revealed eight different patterns of fragments containing zeta-globin genes. The large BamHI fragments containing genes zeta 0 and zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary in size. In contrast to this constancy in the size of the restriction fragments, the copy number of the zeta 2 and zeta 3 genes does vary among different rabbits. No length polymorphism was detected in the BamHI fragments containing the theta-globin genes, but again the copy number varies for restriction fragments containing the theta 2 gene. The alpha 1- and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI fragment. The combined data from hybridization with both zeta and theta probes shows that the BamHI cleavage pattern does not vary within the region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern genomic blot-hybridization patterns for the progeny of parental rabbits with different zeta-globin gene patterns shows that the polymorphic patterns are inherited in a Mendelian fashion. Two different haplotypes have been mapped based on the genomic blot-hybridization data. The variation in the alpha-like globin gene cluster in the rabbit population results both from differences in the copy number of the duplication block containing the zeta-zeta-theta gene set and from the presence or absence of polymorphic BamHI sites.   相似文献   
3.
In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.   相似文献   
4.
We have analyzed the targeting frequencies and recombination products generated with isogenic vectors at the fah and fgr loci in embryonic stem cells. A single vector which could be linearized at different sites to generate either a replacement or an insertion vector was constructed for each locus. A replacement event predominated when the vectors were linearized at the edge of the homologous sequences, while an insertion event predominated when the vectors were linearized within the homologous sequences. However, the ratio of the targeting frequencies exhibited by the different vector configurations differed for the two loci. When the fgr vector was linearized as an insertion vector, the ratio of targeted to random integrations was four- to eightfold greater than when the vector was linearized as a replacement vector. By contrast, the ratio of targeted to random integrations at the fah locus did not vary with the linearization site of the vector. The different relationships between the targeting frequency and the vector configuration at the fgr and fah loci may indicate a DNA sequence or chromatin structure preference for different targeting pathways.  相似文献   
5.
Three Rhizobium japonicum strains and two slow-growing cowpea-type Rhizobium strains were found to remain viable and able to rapidly modulate their respective hosts after being stored in purified water at ambient temperatures for periods of 1 year and longer. Three fast-growing Rhizobium species did not remain viable under the same water storage conditions. After dilution of slow-growing Rhizobium strains with water to 10(3) to 10(5) cells ml-1, the bacteria multiplied until the viable cell count reached levels of between 10(6) and 10(7) cells ml-1. The viable cell count subsequently remained fairly constant. When the rhizobia were diluted to 10(7) cells ml-1, they did not multiply, but full viability was maintained. If the rhizobia were washed and suspended at 10(9) cells ml-1, viability slowly declined to 10(7) cells ml-1 during 9 months of storage. Scanning electron microscopy showed that no major morphological changes took place during storage. Preservation of slow-growing rhizobia in water suspensions could provide a simple and inexpensive alternative to current methods for the preservation of rhizobia for legume inoculation.  相似文献   
6.
Linkage analysis of 146 informative families for MN and Ss resulted in an estimate of the recombination frequency greater than previously reported. Our total is 7 recombinant children out of 467 individuals, including 1 confirmed recombinant (retested and HLA-compatible) and 6 not verified. The 95% confidence interval of our estimate of recombination is 0.0033-0.0167. Our results are compared with two earlier studies.  相似文献   
7.
Summary A newly developed electrophoretic technique for human galactose-1-phosphate uridyl transferase confirms the multiple band patterns for the Duarte and Los Angeles variants. This represents the first confirmation for the Los Angeles variant. The observed frequencies of N, D, and LA types are similar to earlier reports for these variants.  相似文献   
8.
Twelve information bone marrow transplants, with at least one difference in ABO and/or Lewis types between donor and recipient, were retrospectively studied. ABH and Lewis antigens were determined in plasma, erythrocytes, and lymphocytes. Donor lymphocytes acquired the ABH and Lewis antigens from the recipient's plasma in the same way that donor erythrocytes acquired the Lewis antigens from it. Lymphocytotoxicity detected type 1 ABH and Lewis antigens only, providing evidence for the existence of combined ABH and Lewis antigens on lymphocytes. This was in contrast with the ABH antigens on type 2 chains of red cells, which are devoid of Lewis specificities. The differences in genetic control, probable chemical structure, and cellular origin of these two types of ABH antigens are presented in a theoretical model that accounts for most of the known data.  相似文献   
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