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71.
P D Nguyen E A O'Rear A E Johnson R Lu B M Fung 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1989,192(3):261-269
The clot-lysing ability of streptokinase (SK) was examined using membrane-bound thrombi. Encapsulation of SK in large unilamellar phospholipid vesicles (liposomes) resulted in entrapping approximately 30% of its original activity. Measurements of streptokinase activity for liposomal-encapsulated streptokinase (LESK) indicated little loss of activity or leakage in Tris-buffered saline over a 24-hr period at temperatures of 4 and 23 degrees C. However, incubation of free SK and LESK in platelet-poor plasma (PPP) at 37 degrees C resulted in a decrease of SK activity. The retention of SK activity in LESK was considerably higher than that of unentrapped SK. Clot-dissolving time (CDT) was measured by monitoring the pressure drop during slow filtration in plasma through membrane-bound thrombi. The results indicated that both LESK and free SK were able to activate the fibrinolytic system. Without prior incubation in PPP at 37 degrees C, the CDT of a SK and PPP mixture (SK/PPP) was 10.7 +/- 1.9 min (n = 12), while that of a LESK and PPP mixture (LESK/PPP) was 12.4 +/- 1.7 min (n = 12). The CDT-detected clot-lysing abilities of both SK and LESK were diminished by incubation in PPP, but to different extents. After 15- and 30-min incubations, the CDT of SK/PPP increased significantly to 15.5 +/- 1.5 and 24.1 +/- 2.4 min (n = 5, P less than 0.05), respectively. In contrast, the CDT of LESK/PPP increased to 13.3 +/- 0.8 min (n = 5) after 15 min of incubation and to 16.0 +/- 1.1 min (n = 5, P less than 0.05) after a 30-min incubation. These results suggest that entrapment of SK in liposomes preserves the thrombolytic potential of the plasminogen activator by limiting its exposure to the components of the plasma. 相似文献
72.
X. M. Shang H. T. Nguyen R. C. Jackson 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(1):84-94
Summary Heterochromatin differentiation, including band size, sites, and Giemsa staining intensity, was analyzed by the HKG (HCl-KOH-Giemsa) banding technique in the A genomes of 21 diploid (Triticum urartu, T. boeoticum and T. monococcum), 13 tetraploid (T. araraticum, T. timopheevi, T. dicoccoides and T. turgidum var. Dicoccon, Polonicum), and 7 cultivars of hexaploid (T. aestivum) wheats from different germplasm collections. Among wild and cultivated diploid taxa, heterochromatin was located mainly at centromeric regions, but the size and staining intensity were distinct and some accessions' genomes had interstitial and telomeric bands. Among wild and cultivated polyploid wheats, heterochromatin exhibited bifurcated differentiation. Heterochromatinization occurred in chromosomes 4At and 7At and in smaller amounts in 2At, 3At, 5At, and 6At within the genomes of the tetraploid Timopheevi group (T. araraticum, and T. timopheevi) and vice versa within those of the Emmer group (T. dicoccoides and T. turgidum). Similar divergence patterns occurred among chromosome 4Aa and 7Aa of cultivars of hexaploid wheat (T. aestivum). These dynamic processes could be related to geographic distribution and to natural and artifical selection. Comparison of the A genomes of diploid wheats with those of polyploid wheats shows that the A genomes in existing diploid wheats could not be the direct donors of those in polyploid wheats, but that the extant taxa of diploids and polyploids probably have a common origin and share a common A-genomelike ancestor.Contribution of the College of Agricultural Sciences, Texas Tech Univ. Journal No. T-4-233. 相似文献
73.
In Bolivia, the dog is involved in the cycle of visceral leishmaniasis (Leishmania (Le.) chagasi) in the Yungas (alt. 1,000-2,000 m), and also in the cycle of cutaneous leishmaniasis (Le. (V.) braziliensis) in the Alto Beni (alt. 400-600 m). But it plays a different role in the two cycles. In the Yungas focus, it is the main reservoir of Le. (Le.) chagasi and the source of contamination for man. In the Alto Beni focus, it is only a "victim-host", like man, of Le. (V.) braziliensis; the reservoir of which is unknown. Wild mammals are very likely to be involved. 相似文献
74.
Cloning of a lymphocyte homing receptor reveals a lectin domain 总被引:72,自引:0,他引:72
L A Lasky M S Singer T A Yednock D Dowbenko C Fennie H Rodriguez T Nguyen S Stachel S D Rosen 《Cell》1989,56(6):1045-1055
Lymphocytes express cell surface molecules, termed homing receptors, that mediate their selective attachment to specialized high endothelial venules found within secondary lymphoid organs. Previous work has demonstrated that the adhesive interaction between lymphocytes and the endothelium of peripheral lymph nodes appears to involve a lectin-like activity. Moreover, MEL-14, a monoclonal antibody that blocks lymphocyte-peripheral lymph node binding and presumably recognizes the homing receptor mediating this adhesive interaction, appeared to detect the lectin-like receptor. In this paper we describe the cloning of a murine cDNA that encodes the antigen recognized by the MEL-14 antibody. Characterization of the cDNA encoding the putative mouse peripheral lymph node-specific homing receptor shows that it contains a lectin domain that appears to be involved in the binding of lymphocytes to peripheral lymph node endothelium, thus defining a new type of cellular adhesion molecule. This result supports a novel mechanism for the distribution of lymphocyte populations to various lymphoid organs. 相似文献
75.
Green cybrids with a new nucleus-chloroplast combination cannot be selected after protoplast fusion in the intersubfamilial Nicotiana-Solanum combination. As an approach to overcome the supposed plastomegenome incompatibility, a partial plastome transfer by genetic recombination has been considered. After fusions of protoplasts of a light-sensitive Nicotiana tabacum (tobacco) plastome mutant and lethally irradiated protoplasts of wild-type Solanum tuberosum (potato), a single green colony was recovered among 2.5×104 colonies. The regenerated plants had tobacco-like (although abnormal) morphology, but were normally green, and sensitive to tentoxin, demonstrating chloroplast markers of the potato parent. Restriction enzyme analysis of the chloroplast DNA (cpDNA) revealed recombinant, nonparental patterns. A comparison with physical maps of the parental cpDNA demonstrated the presence of a considerable part of the potato plastome flanked by tobacco-specific regions. This potacco plastome proved to be stable in backcross and backfusion experiments, and normally functional in the presence solely of N. tabacum nucleus. 相似文献
76.
Sequence divergence and open regions of RNA secondary structures in the envelope regions of the 17 human immunodeficiency virus isolates. 总被引:4,自引:2,他引:2
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Genetic variation during the course of infection of an individual is a remarkable feature of the acquired immune deficiency syndrome (AIDS) disease. This variation has been studied for the envelope protein encoding regions of seventeen different sequences from various isolates of human immunodeficiency virus (HIV) using multiple sequence comparison and calculation of variability. The open regions with little intramolecular base pairing in these envelope sequences are predicted by a recently developed statistical method. The minimum length L for a run of hypervariable sites, conserved sites, or open regions that gives significance at the 1% (or 0.1%) level is then determined by a scan statistical method. The results show that significant clusters of open regions predicted at the RNA levels correlate with significant clusters of hypervariable sites in the HIV envelope gene. Those significant genomic variations in HIVs seem to be manifested mainly in the extracellular portion of the envelope protein. Twelve potential antigenic determinants are predicted using an antigenic index method. Interestingly, the majority of the significant hypervariable regions in the exterior envelope protein (gp120) were predicted potential epitopes. 相似文献
77.
Purification and properties of the DNA-binding protein HPB12 from Bacillus subtilis nucleoid 总被引:2,自引:0,他引:2
We report the purification to homogeneity of a 12 KDa protein (HPB12) present in the nucleoids of Bacillus subtilis. From the purification data the abundance of the protein was estimated to about 20,000 monomers per cell. The HPB12 protein is heat-stable and acid-soluble and binds preferentially to supercoiled and linearized double-stranded DNAs. The binding of the protein to the supercoiled DNA occurs very rapidly and appears to be cooperative. Moreover, the complexes are extremely stable and do not dissociate after 90 min. These properties are consistent with a role of the HPB12 protein in the structure of the B. subtilis chromosome. 相似文献
78.
The immobilization of penicillin G acylase on chitosan 总被引:3,自引:0,他引:3
79.
Permeability of human granulocytes to dimethyl sulfoxide 总被引:1,自引:0,他引:1
The permeability of the membrane of human granulocytes to the permeating solute dimethyl sulfoxide (DMSO) was studied using the Onsager form of the phenomenological equations derived from the theory of irreversible thermodynamics. Changes in cellular volume were monitored with an electronic particle counter as samples of that population were introduced into hypertonic osmotica. Temperature and concentration sensitivity analyses of the permeability coefficients were carried out. It is shown that the introduction of the Onsager formalism allows further insight into the observed transport phenomena. It was found that DMSO may affect the water permeability properties of the membrane for that population of cells. 相似文献
80.
Pathophysiological variations in the rat liver plasma membrane serine proteinase activity 总被引:2,自引:0,他引:2
The effects of fasting, diabetes, cholestasis, two-third hepatectomy and adrenalectomy on the rat liver plasma membrane serine proteinase activity were studied. Our results show a significant decrease of the enzyme activity during fasting (-50%), during experimental diabetes (-50%), in regenerating liver after partial hepatectomy (-70%) and after extrahepatic cholestasis (-70%). No modifications are noted when the rats are bilaterally adrenalectomized. These findings suggest that the enzyme activity may be linked to the level of circulating insulin, and may be regulated in physiological cellular proliferation so as to prevent undesirable protein degradation. 相似文献