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21.
A Cu-sensitive mutant, cup1-1, of Arabidopsis thaliana has a pattern of heavy-metal sensitivity different from that of the cad1 and cad2 mutants, which are deficient in phytochelatin biosynthesis. The latter are significantly sensitive to Cd and Hg and only slightly sensitive to Cu, whereas the cup1-1 mutant is significantly sensitive to Cu, slightly sensitive to Cd, and not more sensitive to Hg, compared to the wild type. Genetic analysis has shown that the sensitive phenotype is recessive to the wild type and segregates as a single Mendelian locus, which has been mapped to chromosome 1. Genetic and biochemical studies demonstrate that the cup1-1 mutant is not affected in phytochelatin biosynthesis or function. The sensitive phenotype of the cup1-1 mutant is associated with, and probably due to, increased accumulation of higher levels of Cd and Cu compared with the wild type. Consistent with this, a Cu-inducible, root-specific metallothionein gene, MT2a, is expressed in cup1-1 roots under conditions in which it is not expressed in the wild type. Undifferentiated cup1-1 callus tissue did not show the Cu-sensitive phenotype, suggesting that the mutant phenotype, in contrast to cad1 and cad2, is not expressed at the cellular level. 相似文献
22.
The morphological plasticity of astrocytes from the subfornical organ of the adult rat has been examined using an explant culture preparation. Astrocytes migrate out of the explant and form a monolayer of amorphous, non-stellate cells. This non-stellate form was maintained when cultures were incubated in a HEPES buffered salt solution (HBSS) for 50 minutes. The fraction of cells that was stellate in these cultures was significantly increased when cultures were incubated in HBSS supplemented with forskolin (5 μM; but not 1,9-dideoxyforskolin) or with nitroprusside (10–100μM)indicating that elevation of intracellular cAMP or cGMP mediates stellation. The stellation responses induced by forskolin and by nitroprusside were blocked by inclusion of serum (0.5%) or of LY83,583 (10μM), an inhibitor of soluble guanylate cyclase, in the incubation medium. The relevance of the data to neuroglial plasticity in the subfornical organ in vivo is discussed. 相似文献
23.
The regulatory region of the aroF-tyrA operon was fused to the chloramphenicol acetyltransferase (cat) gene on a plasmid vector. Expression of the cat gene was subject to repression by tyrR+. This fusion was used to isolate regulatory mutants with increased expression of the cat gene in which repression by tyrR+ was affected. Nucleotide sequencing of these mutants has led to the identification of three sites involved in the repression of aroF by tyrR+. The existence of a functional promoter divergently transcribing from the aroF regulatory region was also demonstrated by using the cat fusion vector. The expression of this promoter is also regulated by tyrR+. 相似文献
24.
Formation of a lambda (Tn10) tyrR+ specialized transducing bacteriophage from Escherichia coli K-12. 总被引:8,自引:7,他引:1
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The transposon Tn10, coding for resistance to tetracycline, was inserted close to the tyrR+ gene at min 28 on the Escherichia coli chromosome. The homology between this transposon and a lambda (Tn10) phage was employed to direct integration of lambda close to tyrR+ with subsequent isolation of a lambda (Tn10) tyrR+ transducing phage. Results of restriction endonuclease analysis of the transducing phage are presented. 相似文献
25.
STEFAN I. CSÖGÖR 《Nature: New biology》1972,238(87):287-288
CHOLESTEROL is found in the blood as a structural component of lipoproteins concerned with the transport of other lipids1. The high resolution nuclear magnetic resonance spectra of high density serum lipoproteins are similar to that observed when lipids are dissolved in organic solvents, or dispersed in water by bile salts or detergents, or in sonicated form. The lipid component in lipoproteins is therefore probably in an extremely fluid condition2. If human serum is mixed with paraffin oil, some of the cholesterol diffuses into the oil without affecting the ultraviolet absorption spectrum of serum proteins. This procedure avoids any protein denaturing action used for cholesterol extraction3–5. It therefore seems that serum cholesterol has two fractions, one strongly bound by lipoprotein structures and the other loosely bound and diffusible in an oil phase. In this article I designate the loosely bound fraction “diffusible”. 相似文献
26.
The arabinose kinase,ARA1, gene of Arabidopsis is a novel member of the galactose kinase gene family
Sherson Sarah Gy Isabelle Medd Jonathan Schmidt Renate Dean Caroline Kreis Martin Lecharny Alain Cobbett Christopher 《Plant molecular biology》1999,39(5):1003-1012
The arabinose-sensitive ara1-1 mutant of Arabidopsis is deficient in arabinose kinase activity. A candidate for the ARA1 gene, ISA1, has been previously identified through the Arabidopsis genome sequencing initiative. Here we demonstrate that (1) the ARA1 gene coincides with ISA1 in a positional cloning strategy; (2) there are mutations in the ISA1 gene in both the ara1-1 mutant and an intragenic suppressor mutant; and (3) the ara1-1 and suppressor mutant phenotypes can be complemented by the expression of the ISA1 cDNA in transgenic plants. Together these observations confirm that ISA1 is the ARA1 gene. ARA1 is a member of the galactose kinase family of genes and represents a new substrate specificity among this and other families of sugar kinases. A second gene with similarities to members of the galactose kinase gene family has been identified in the EST database. A 1.8 kb cDNA contained an open reading-frame predicted to encode a 496 amino acid polypeptide. The GAL1 cDNA was expressed in a galK mutant of Escherichia coli and in vitro assays of extracts of the strain expressing GAL1 confirmed that the cDNA encodes a galactose kinase activity. Both GAL1 and ARA1 cross-hybridise at low stringency to other sequences suggesting the presence of additional members of the galactose kinase gene family. 相似文献
27.
Ciro Coletta Katalin Módis Bartosz Szczesny Attila Brunyánszki Gábor Oláh Ester CS Rios Kazunori Yanagi Akbar Ahmad Andreas Papapetropoulos Csaba Szabo 《Molecular medicine (Cambridge, Mass.)》2015,21(1):1-14
Hydrogen sulfide (H2S), as a reducing agent and an antioxidant molecule, exerts protective effects against hyperglycemic stress in the vascular endothelium. The mitochondrial enzyme 3-mercaptopyruvate sulfurtransferase (3-MST) is an important biological source of H2S. We have recently demonstrated that 3-MST activity is inhibited by oxidative stress in vitro and speculated that this may have an adverse effect on cellular homeostasis. In the current study, given the importance of H2S as a vasorelaxant, angiogenesis stimulator and cellular bioenergetic mediator, we first determined whether the 3-MST/H2S system plays a physiological regulatory role in endothelial cells. Next, we tested whether a dysfunction of this pathway develops during the development of hyperglycemia and μmol/L to diabetes-associated vascular complications. Intraperitoneal (IP) 3-MP (1 mg/kg) raised plasma H2S levels in rats. 3-MP (10 1 mmol/L) promoted angiogenesis in vitro in bEnd3 microvascular endothelial cells and in vivo in a Matrigel assay in mice (0.3–1 mg/kg). In vitro studies with bEnd3 cell homogenates demonstrated that the 3-MP-induced increases in H2S production depended on enzymatic activity, although at higher concentrations (1–3 mmol/L) there was also evidence for an additional nonenzymatic H2S production by 3-MP. In vivo, 3-MP facilitated wound healing in rats, induced the relaxation of dermal microvessels and increased mitochondrial bioenergetic function. In vitro hyperglycemia or in vivo streptozotocin diabetes impaired angiogenesis, attenuated mitochondrial function and delayed wound healing; all of these responses were associated with an impairment of the proangiogenic and bioenergetic effects of 3-MP. The antioxidants dl-α-lipoic acid (LA) in vivo, or dihydrolipoic acid (DHLA) in vitro restored the ability of 3-MP to stimulate angiogenesis, cellular bioenergetics and wound healing in hyperglycemia and diabetes. We conclude that diabetes leads to an impairment of the 3-MST/H2S pathway, and speculate that this may contribute to the pathogenesis of hyperglycemic endothelial cell dysfunction. We also suggest that therapy with H2S donors, or treatment with the combination of 3-MP and lipoic acid may be beneficial in improving angiogenesis and bioenergetics in hyperglycemia. 相似文献
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Acetylcholine (ACh), the first neurotransmitter to be identified, regulate the activities of central and peripheral functions
through interactions with muscarinic receptors. Changes in muscarinic acetylcholine receptor (mAChR) have been implicated
in the pathophysiology of many major diseases of the central nervous system (CNS). Previous reports from our laboratory on
streptozotocin (STZ) induced diabetic rats showed down regulation of muscarinic M1 receptors in the brainstem, hypothalamus,
cerebral cortex and pancreatic islets. In this study, we have investigated the changes of acetylcholine esterase (AChE) enzyme
activity, total muscarinic and muscarinic M1 receptor binding and gene expression in the corpus striatum of STZ – diabetic
rats and the insulin treated diabetic rats. The striatum, a neuronal nucleus intimately involved in motor behaviour, is one
of the brain regions with the highest acetylcholine content. ACh has complex and clinically important actions in the striatum
that are mediated predominantly by muscarinic receptors. We observed that insulin treatment brought back the decreased maximal
velocity (Vmax) of acetylcholine esterase in the corpus striatum during diabetes to near control state. In diabetic rats there was a decrease
in maximal number (Bmax) and affinity (Kd) of total muscarinic receptors whereas muscarinic M1 receptors were increased with decrease in affinity in diabetic rats.
We observed that, in all cases, the binding parameters were reversed to near control by the treatment of diabetic rats with
insulin. Real-time PCR experiment confirmed the increase in muscarinic M1 receptor gene expression and a similar reversal
with insulin treatment. These results suggest the diabetes-induced changes of the cholinergic activity in the corpus striatum
and the regulatory role of insulin on binding parameters and gene expression of total and muscarinic M1 receptors. 相似文献