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41.
Five patients with asexual and sexual parasites of Plasmodium vivax were treated orally with 600 mg chloroquine diphosphate (hour 0) followed with 300 mg at 8, 24 and 48 h later. Primaquine phosphate, 15 mg, was administered concurrently at h 0 and at 24 h intervals for 14 days. Anopheles darlingi were fed before the first dose (h -0.5) and 0.5, 1, 2, 4, 6, 8, 10, 12, 16, 20, 24, 36, 48, 60 and 72 h later. Mosquitoes were examined for oocysts on day 8 and for sporozoites on day 15 after infection. Four of the five patients studied were still infective to mosquitoes from 1-5 h after the first dose of chloroquine plus primaquine. One of these and one other patient, who vomited 15 min after the first dose, became infective again at hours 10 and 12, respectively. Once produced, oocysts in mosquitoes fed on patients before, during and after chloroquine plus primaquine treatment appeared normal and produced sporozoite infected salivary glands. In view of these data, it is concluded that primaquine demonstrated rapid gametocytocidal activity and should be administered concurrently with chloroquine to reduce vivax malaria transmission. 相似文献
42.
CD4-like molecules in human sperm 总被引:5,自引:0,他引:5
The expression of a molecule recognized by CD4 monoclonal antibodies was investigated on human sperm using immunolabelling, biochemical and immunochemical methods. Flow cytometry detected a significant fluorescence signal. SDS-PAGE analysis and Western blotting identified a molecule of 60 kDa, consistent with a CD4-like structure as confirmed after selective immunoseparation. Additional bands reacting with anti-CD4 were found in sperm extracts (73 kDa) and seminal fluid (90 kDa). These data indicate that sperm express a molecule similar to the receptor for HIV described on mononuclear cells. 相似文献
43.
Evidence for allosteric coupling between the ribosome and repressor binding sites of a translationally regulated mRNA 总被引:8,自引:0,他引:8
Escherichia coli ribosomal protein S4 is a translational repressor regulating the expression of four ribosomal genes in the alpha operon. In vitro studies have shown that the protein specifically recognizes an unusual mRNA pseudoknot secondary structure which links sequences upstream and downstream of the ribosome binding site for rpsM (S13) [Tang, C. K., & Draper, D. E. (1989) Cell 57, 531]. We have prepared fusions of the rpsM translational initiation site and lacZ that allows us to detect repression in cells in which overproduction of S4 repressor can be induced. Twenty-five mRNA sequence variants have been introduced into the S13-lacZ fusions and the levels of translational repression measured. Sets of compensating base changes confirm the importance of the pseudoknot secondary structure for translational repression. An A residue in a looped, single-stranded sequence is also required for S4 recognition and may contact S4 directly. Comparison of translational repression levels and S4 binding constants for the set of mRNA mutations show that nine mutants are repressed much more weakly than predicted from their affinity for S4; in extreme cases no repression can be detected for variants with unchanged S4 binding. We suggest that the mRNA contains functionally distinct ribosome and repressor binding sites that are allosterically coupled. Mutations can relieve translational repression by disrupting the linkage between the two sites without altering S4 binding. This proposal assigns to the mRNA a more active role in mediating translational repression than found in other translational repression systems. 相似文献
44.
Bulge loops are commonly found in helical segments of cellular RNAs. When incorporated into long double-stranded RNAs, they may introduce points of flexibility or permanent bend that can be detected by the altered electrophoretic gel mobility of the RNA. We find that a single An or Un bulge loop near the middle of a long RNA helix significantly retards the RNA during polyacrylamide gel electrophoresis if n greater than or equal to 2. The mobility of an RNA containing two A2 bulges various periodically with the number of base pairs between the bulges. We interpret this to mean that A2 bulges varies periodically with the number of base pairs between the bulges. We interpret this to mean that Z2 bulges form torsionally stiff bends in the helix; the gel mobility reaches a minimum when the total helical twist between the bulges rotates the arms of the molecule into a cis conformation. The gel mobilities are proportional to the predicted end-to-end distance of the RNA if the average RNA helical repeat is 11.8 +/- 0.2 bp/turn and there is no helical twist (3 +/- 9 degrees) associated with the bulge (data obtained in 0.15 M Na+). Other sizes and sequences of bulges have very different effects on RNA helix conformation and flexibility. U2 bulges bend the helix to a much smaller degree than A2 bulges, while longer A or U bulge sequences probably allow bends of 90 degrees or more; all of these may be fairly flexible joints.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
45.
We examined various media and conditions to isolate symbiotic cyanobacteria from the leaf cavities of Azolla spp. Cyanobacteria survived and multiplied to a limited extent on a medium with fructose, Casamino Acids, yeast extract, and NaNO3 under 1% O2. These cyanobacteria were antigenically identical to the endosymbionts. 相似文献
46.
Olivia Hanson-Painton Martin J. Griffin Jordan Tang 《Biochemical and biophysical research communications》1981,101(4):1364-1371
Solutions of cytosolic proteins from rat liver contain benzo(a)pyrene solubilizing activity capable of serving as a carrier between solid state benzo(a)pyrene and microsomal cytochrome P450. Fractionation of benzo(a)pyrene-saturated cytosolic proteins on a Sephadex G-100 column or by sucrose density gradients produced benzo(a)pyrene peaks of about 46,000 daltons and a very high molecular weight material. The protein-bound benzo(a)pyrene obtained in both peaks was oxidized rapidly by microsomes in the presence of NADPH, indicating that the benzo(a)pyrene carrier activity is capable of presenting the substrate to the cytochrome P450. Liver cytosolic proteins from rats receiving intraperitoneal injection of [14C] benzo(a)pyrene was chromatographed on a column of Sephadex G-75. Radioactivity eluted at the same positions of the chromatogram as did the carrier activities described above. These results indicate that these benzo(a)pyrene carrier proteins may have an role in the metabolism of benzo(a)pyrene. 相似文献
47.
Proteoglycans from bovine nasal cartilage. Properties of a soluble form of link protein. 总被引:20,自引:0,他引:20
L H Tang L Rosenberg A Reiner A R Poole 《The Journal of biological chemistry》1979,254(20):10523-10531
48.
49.
J Marciniszyn J S Huang J A Hartsuck J Tang 《The Journal of biological chemistry》1976,251(22):7095-7102
Intramolecular pepsinogen activation is inhibited either by pepstatin, a potent pepsin inhibitor, or by purified globin from hemoglobin, a good pepsin substrate. Also, pepsinogen at pH 2 can be bound to a pepstatin-Sepharose column and recovered as native zymogen upon elution in pH 8 buffer. Kinetic studies of the globin inhibition of pepsinogen activation show that globin binds to a pepsinogen intermediate. This interaction gives rise to competitive inhibition of intramolecular pepsinogen activation. The evidence presented in this paper suggests that pepsinogen is converted rapidly upon acidification to the pepsinogen intermediate delta. In the absence of an inhibitor, the intermediate undergoes conformational change to bind the activation peptide portion of this same pepsinogen molecule in the active center to form an intramolecular enzyme-substrate complex (intermediate theta). This is followed by the intramolecular hydrolysis of the peptide bond between residues 44 and 45 of the pepsinogen molecule and the dissociation of the activation peptide from the pepsin. Intermediate delta apparently does not activate another pepsinogen molecule via an intermolecular process. Neither does intermediate delta hydrolyze globin substrate. 相似文献
50.