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Alterations in pp60c-src accompany differentiation of neurons from rat embryo striatum. 总被引:17,自引:9,他引:8
C A Cartwright R Simantov P L Kaplan T Hunter W Eckhart 《Molecular and cellular biology》1987,7(5):1830-1840
Cultured neurons from rat embryo striatum were found to contain two structurally distinct forms of pp60c-src. The 60-kilodalton (kDa) form appeared similar to pp60c-src from cultured rat fibroblasts or astrocytes. The 61-kDa form was specific to neurons and differed in the NH2-terminal 18 kDa of the molecule. In undifferentiated neurons the predominant phosphorylated species of pp60c-src was the fibroblast form. Upon differentiation, a second phosphorylated form of pp60c-src was detected. This form had two or more additional sites of serine phosphorylation within the NH2-terminal 18-kDa region of the molecule, one of which was Ser-12. The specific protein-tyrosine kinase activity of the total pp60c-src population increased 14-fold, as measured by autophosphorylation, or 7-fold, as measured by phosphorylation of an exogenous substrate, as striatal neurons differentiated. This elevation in protein kinase activity occurred without a detectable decrease in Tyr-527 phosphorylation or increase in Tyr-416 phosphorylation. Our results support the idea that the expression of the neuron-specific form of pp60c-src and the increase in specific protein kinase activity may be important for neuronal differentiation. 相似文献
3.
The response to high concentrations of B in soil was compared for Triticum aestivum L. (vars. Chinese Spring and Halberd) and the amphiploid of Chinese Spring × Agropyron elongatum (Host). The tolerance of the three genotypes, with respect to yield at the high B treatments, was amphipolid>Halberd>Chinese Spring. The concentration of B in whole shoots was similar for the amphiploid and Halberd and significantly higher for Chinese Spring. The mechanism for tolerance to B appears to be the same for the amphiploid and wheat and is related to reduced accumulation of B in shoots. 相似文献
4.
Ejaculated, bovine sperm have been subjected to multiple partition in aqueous two-phase systems. This partition, carried out in a countercurrent fashion, reveals heterogeneity of the sperm population with respect to surface properties. The sperm, when partitioned in phase systems that detect non-change associated surface properties (change-insensitive) are largely distributed as two distinct populations. In charge-sensitive phase systems (which principally detect cell surface molecules carrying charge) the sperm do not show any obvious surface heterogeneity. Considerable heterogeneity is revealed in affinity-ligand phase systems containing palmitic acid coupled to one of the phase components-poly(ethylene glycol). There is a difference in surface heterogeneity between sperm which have been washed in buffer or left unwashed, direct from the ejaculate. This is indicative of weak adsorption of proteins to the sperm surface in seminal fluid. These results show that bovine ejaculated sperm is a heterogeneous cell population having unequal distributions of a number of different surface molecules. 相似文献
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Purification and properties of two glyoxylate reductases from a species of Pseudomonas 总被引:1,自引:1,他引:0 下载免费PDF全文
1. Two enzymes that catalyse the reduction of glyoxylate to glycollate have been separated and purified from a species of Pseudomonas. Their molecular weights were estimated as 180000. 2. Reduced nicotinamide nucleotides act as the hydrogen donators for the enzymes. The NADH-linked enzyme is entirely specific for its coenzyme but the NADPH-linked reductase shows some affinity towards NADH. 3. Both enzymes convert hydroxypyruvate into glycerate. 4. The glyoxylate reductases show maximal activity at pH6·0–6·8, are inhibited by keto acids and are strongly dependent on free thiol groups for activity. 5. The Michaelis constants for glyoxylate and hydroxypyruvate were found to be of a high order. 6. The reversibility of the reaction has been demonstrated for both glyoxylate reductases and the equilibrium constants were determined. 7. The reduction of glyoxylate and hydroxypyruvate is not stimulated by anions. 相似文献
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Kenneth T. Izutsu Sahba Fatherazi Carol M. Belton Dolphine Oda Frank D. Cartwright George E. Kenny 《In vitro cellular & developmental biology. Animal》1996,32(6):361-365
Summary The relations between K+ channel and Cl− channel currents and mycoplasma infection status were studied longitudinally in HSG cells, a human submandibular gland cell
line. The K+ channel currents were disrupted by the occurrence of mycoplasma infection: muscarinic activation of K+ channels and K+ channel expression as estimated by ionomycin- or hypotonically induced K+ current responses were all decreased. Similar decreases in ionomycin- and hypotonically induced responses were observed for
Cl− channels, but only the latter decrease was statistically significant. Also, Cl− currents could be elicited more frequently than K+ currents (63% of cases versus 0%) in infected cells when tested by exposure to hypotonic media, indicating that mycoplasma
infection affects K+ channels relatively more than Cl− channels. These changes occurred in the originally infected cells, were ameliorated when the infection was cleared with sparfloxacin,
and recurred when the cells were reinfected. Such changes would be expected to result in hyposecretion of salivary fluid if
they occurredin vivo. 相似文献
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The nucleotide sequence of oocyte 5S DNA in Xenopus laevis. II. The GC-rich region 总被引:50,自引:0,他引:50
The primary sequence of the GC-rich half of the repeating unit in X. laevis 5S DNA has been determined in both a single plasmid-cloned repeating unit and in the total population of repeatig units. The GC-rich half of the repeating unit contains a single long duplication of 174 nucleotides. The duplicated segment commences 73 nucleotides preceding the 5' end of the gene and terminates at nucleotide 101 of the gene. The duplicated portion of the gene, termed the pseudogene, differs by 10 nucleotides from the corresponding portion of the gene, and the remaining duplicated sequence of 73 nucleotides differs by 13 nucleotides. The plasmid-cloned repeating unit differs from the dominant sequence in the total population repeating units by 6 nucleotides in the GC-rich region. Evidence is provided that most of the CpG dinucleotides in 5S DNA are at least partially methylated. 相似文献