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131.
Cholinomimetics Increase Glutamate Outflow via an Action on the Corticostriatal Pathway: Implications for Alzheimer's Disease 总被引:3,自引:0,他引:3
Sas N. Dijk Paul T. Francis Gary C. Stratmann David M. Bowen 《Journal of neurochemistry》1995,65(5):2165-2169
Abstract: Physostigmine, the acetylcholinesterase inhibitor (0.3 mg/kg, i.m.), increased extracellular glutamate but not aspartate concentrations in the striatum of anaesthetised rats, determined using microdialysis and HPLC. The rise was both tetrodotoxin and calcium dependent. In contrast, neither physostigmine (10 µ M ) added to the perfusion fluid nor vehicle (injected intramuscularly) affected amino acid concentrations. To obtain evidence that the action of acetylcholine was to modulate positively cortical pyramidal neurone activity via the M1 receptor, the selective M1 agonist PD 142505-0028 (10 µ M ) was topically applied to the frontal cortex. Like physostigmine, PD 142505-0028 rapidly increased glutamate but not aspartate concentrations in the striatum. Moreover, the effect of intramuscular physostigmine was blocked by a topically applied M1 antagonist. These new data add to our hypothesis that cholinomimetics increase pyramidal neurone function. 相似文献
132.
Each cryptomonad strain contains only a single spectroscopic type of biliprotein. These biliproteins are isolated as 50000 kDa '2 complexes which carry one bilin on the and three on the subunit. Six different bilins are present on the cryptomonad biliproteins, two of which (phycocyanobilin and phycoerythrobilin) also occur in cyanobacterial and rhodophytan biliproteins, while four are known only in the cryptomonads. The subunit is encoded on the chloroplast genome, whereas the subunits are encoded by a small nuclear multigene family. The subunits of all cryptomonad biliproteins, regardless of spectroscopic type, have highly conserved amino acid sequences, which show > 80% identity with those of rhodophytan phycoerythrin subunits. In contrast, cyanobacteria and red algal chloroplasts each contain several spectroscopically distinct biliproteins organized into macromolecular complexes (phycobilisomes). The data on biliproteins, as well as several other lines of evidence, indicate that the cryptomonad biliprotein antenna system is primitive and antedates that of the cyanobacteria. It is proposed that the gene encoding the cryptomonad biliprotein subunit is the ancestral gene of the gene family encoding cyanobacterial and rhodophytan biliprotein and subunits.Abbreviations Chl
chlorophyll
- CER
chloroplast endoplasmic reticulum
- SSU rRNA
small subunit ribosomal RNA 相似文献
133.
Characterization of a Chlamydomonas reinhardtii gene encoding a protein of the DNA photolyase/blue light photoreceptor family 总被引:6,自引:0,他引:6
The organization and nucleotide sequence of a gene from Chlamydomonas reinhardtii encoding a member of the DNA photolyase/blue light photoreceptor protein family is reported. A region of over 7 kb encompassing the gene was sequenced. Northern analysis detected a single 4.2 kb mRNA. The gene consists of eight exons and seven introns, and encodes a predicted protein of 867 amino acids. The first 500 amino acids exhibit significant homology with previously sequenced DNA photolyases, showing the closest relationship to mustard (Sinapis alba) photolyase (43% identity). An even higher identity, 49%, is obtained when the Chlamydomonas gene product is compared to the putative blue-light photoreceptor (HY4) from Arabidopsis thaliana. Both the Chlamydomonas and the Arabidopsis proteins differ from the well characterized DNA photolyases in that they contain a carboxyl terminal extension of 367 and 181 amino acids, respectively. However, there is very little homology between the carboxyl terminal domains of the two proteins. A previously isolated Chlamydomonas mutant, phrl, which is deficient in DNA photolyase activity, especially in the nucleus, was shown by RFLP analysis not to be linked to the gene we have isolated. We propose this gene encodes a candidate Chlamydomonas blue light photoreceptor. 相似文献
134.
135.
136.
Limitations to net photosynthesis as affected by nitrogen status in jack pine (Pinus banksiana Lamb.) seedlings 总被引:2,自引:0,他引:2
Relative limitations of nitrogen (N) status on the processescontributing to photosynthetic rate (A) were investigated. Jackpine {Pinus banksiana Lamb.) seedlings from seeds grown in sandculture were supplied with four different N treatments for 6weeks, which resulted in a needle N content ranging from 5085mmol m2 (1432 mg g1 dry weight). Leaf gasexchange at varying CO2 levels was measured and limitationson A350 (A at ambient CO2 level) caused by finite, limitingcarboxylation efficiency (c.e.), maximum A (Amax)and stomatalconductance were estimated from an analysis of the responseof A to internal CO2 concentration. Although c.e. and Amax decreasedlinearly with the decline in needle N, the magnitudes of theirchanges relative to A350 differed. Amax varied with A350 andalways exceeded A350 by 3738% c.e., however, declinedfaster than A350, as needle N level decreased. Consequently,relative limitation on A350 caused by inefficient Amax remainedconstant, but limitations caused by c.e. increased by 1015%at low N levels. In contrast, the limitation by stomatal conductancedeclined initially, but remained stable when N content droppedbelow 75 mmol m2. The results suggest: (1) a decreasein biochemical capacity, but not stomatal conductance, contributedto the reduction of A350 induced by N-deficiency in jack pineseedlings; and (2) the capacity of carboxylation appeared tobe impaired more than that of electron transport and/or photophosphorylationand its reduction may be the major reason for the reductionin A350. Key words: ACi analysis, carboxylation efficiency, electron transport, nitrogen deficiency, stomatal conductance 相似文献
137.
Anne L. Holleran Donald A. Briscoe Gary Fiskum Joanne K. Kelleher 《Molecular and cellular biochemistry》1995,152(2):95-101
A study was undertaken to assess the role of a physiological concentration of glutamine in AS-30D cell metabolism. Flux of14C-glutamine to14CO2 and of14C-acetate to glutamate was detected indicating reversible flux between glutamate and TCA cycle -ketoglutarate. These fluxes were transaminase dependent. A flux analysis was compared using data from three tracers that label -ketoglutarate carbon 5, [2-14C]glucose, [1-14C]acetate and [5-14C]glutamine. The analysis indicated that the probability of flux of TCA cycle -ketoglutarate to glutamate was, at minimum, only slightly less than the probability of flux of -ketoglutarate through -ketoglutarate dehydrogenase. The apparent Km for oxidative flux of [14C]glutamine to14CO2, 0.07 mM, indicated that this flux was at a maximal rate at physiological, 0.75 mM, glutamine. Although oxidative flux through -ketoglutarate dehydrogenase was the major fate of glutamine, flux of glutamine to lipid via reductive carboxylation of -ketoglutarate was demonstrated by measuring incorporation of [5-14C]glutamine into14C-lipid. In media containing glucose (6 mM), and glutamine (0.75 mM) 47 per cent of the lipid synthesized from substrates in the media was derived from glutamine via reductive carboxylation and 49 per cent from glucose. These findings of nearly equal fluxes suggest that lipogenesis via reductive carboxylation may be an important role of glutamine in hepatoma cells. 相似文献
138.
139.
Alexander A. Bachmanov Danielle R. Reed Yuro Ninomiya Masashi Inoue Michael G. Tordoff R. Arlen Price Gary K. Beauchamp 《Mammalian genome》1997,8(8):545-548
Individual variability in sucrose consumption is prominent in humans and other species. To investigate the genetic contribution
to this complex behavior, we conducted behavioral, electrophysiological, and genetic studies, using male progeny of two inbred
mouse strains (C57BL/6ByJ [B6] and 129/J [129]) and their F2 hybrids. Two loci on Chromosome (Chr) 4 were responsible for over 50% of the genetic variability in sucrose intake. These
loci apparently modulated intake by altering peripheral neural responses to sucrose. One locus affected the response threshold,
whereas the other affected the response magnitude. These findings suggest that the majority of difference in sucrose intake
between male B6 and 129 mice is due to polymorphisms of two genes that influence receptor or peripheral nervous system activity.
Received: 27 January 1997 / Accepted: 17 March 1997 相似文献
140.