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41.
Temporal Profiles of Proteins Responsive to Transient Ischemia 总被引:4,自引:3,他引:1
The responses of long and short half-lived proteins to ischemia were measured in rat brain during 6 days of recovery from 30 min of transient forebrain ischemia produced by four-vessel occlusion. At the end of the ischemic interval, the neocortical activities of four vulnerable enzymes [ornithine (ODC) and S-adenosylmethionine (SAMDC) decarboxylases, and RNA polymerases I and II] were unchanged, but within 30 min of reperfusion, their activities dropped by 25-50%. The loss of substance P in the striatum and substantia nigra was slower, reaching about 50% by 12 h. On the other hand, the activities of 5 long half-lived enzymes did not change in the neocortex at 5 and 15 h of reperfusion and regional protein concentrations were essentially unaffected over 6 days survival. The rate and extent of normalization of the amounts or activities of the vulnerable proteins varied. RNA polymerase II and ODC activities were restored within 4 h, and ODC showed a biphasic increase in activity, with peaks at 10 h and 2-3 days. RNA polymerase I and SAMDC activities were restored by 18 h and 5 days, respectively, whereas substance P concentrations did not completely recover, even at 6-15 days. The greater the regional reduction of blood flow during ischemia, the larger the net change (gain or loss) of SAMDC or ODC activity and the longer the time required to normalize the activities of these enzymes. The average rate of proteolysis, assessed by measuring the rate of clearance of 14C from protein prelabeled with [14C]bicarbonate, was abnormal during the first 2 days of reperfusion. Postischemic changes in both protein synthesis and degradation could affect the amounts of some of the proteins responsive to transient ischemia. 相似文献
42.
Deprenyl Protects Dopamine Neurons from the Neurotoxic Effect of 1-Methyl-4-Phenylpyridinium Ion 总被引:3,自引:2,他引:1
1-Methyl-4-phenylpyridinium ion (MPP+) is the product of the metabolic oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) by monoamine oxidase (MAO). MPP+ is toxic to 3,4-dihydroxyphenylethylamine (dopamine, DA) neurons in explant cultures of rat embryonic midbrain. Addition of 2.5 microM MPP+ to the feeding medium for 6 days results in significant reduction of the DA levels in the cultures (to 19% of control) as well as in the uptake of [3H]DA (to 32% of control). When the cultures are treated with the MAO inhibitor deprenyl (10 microM) 24 h prior to and during exposure to MPP+, the DA neurons are protected from the toxicity of the drug. In the combined deprenyl plus MPP+ treatment, the levels of DA in the cultures remain at the control range and the [3H]DA uptake is reduced to only 73% of control. These results indicate that MAO is involved in the toxicity of MPP+ on DA neurons. 相似文献
43.
Gerald D. Fasman 《Journal of biosciences》1985,8(1-2):15-23
The Chou-Fasman predictive algorithm for determining the secondary structure of proteins from the primary sequence is reviewed.
Many examples of its use are presented which illustrate its wide applicability, such as predicting (a) regions with the potential
for conformational change, (b) sequences which are capable of assuming several conformations in different environments, (c)
effects of single amino acid mutations, (d) amino acid replacements in synthesis of peptides to bring about a change in conformation,
(e) guide to the synthesis of polypeptides with definitive secondary structure,e.g. signal sequences, (f) conformational homologues from varying sequences and (g) the amino acid requirements for amphiphilicα-helical peptides. 相似文献
44.
Gerald S. Manning 《Cell biochemistry and biophysics》1985,7(3):177-184
The equilibrium trajectory of the axis of a rod subject to an externally imposed curved potential energy trough tends to conform
to the shape of the curved trough, but also tends to be straight because of elastic resistance to bending. The actual path
of the axis is a balance between the two extremes. We consider a potential energy trough centered along a circular arc of
radiusR. For a rod of small length compared toR, we show that the axis at equilibrium forms an arc of a circle of radius greater thanR. The value of the radius of the axial path depends on the relative values of the Hooke’s Law bending constant for the rod
and the depth and width of the trough. Motivation for the calculation is provided by nucleosomal DNA, which conforms to the
surface of a roughtly cylindrical histone core at physiological ionic strength, but is observed to unwind into a partially
extended conformation at very low ionic strength. We suggest that the rigidity to bending of short DNA segments becomes sufficiently
great at low ionic strength to overcome attractive interactions with the histone surface. Alternately, of course, if during
the cell cycle mutually attractive forces between DNA and histone core are weakened at constant ionic strength, the same type
of unfolding would be expected to occur as the strength of the DNA-histone contacts drops below the level required to overcome
elastic resistance to bending of the DNA rod. 相似文献
45.
The effects of mineral salts constituting water hardness on fecundity ofDaphnia magna were assessed. Of the salts tested, increased concentrations of NaHCO3 and MgSO4 had no effect on fecundity, CaSO4 significantly increased fecundity, and KCl significantly reduced fecundity. The number of offspring produced per daphnid
was correlative to the CaSO4 concentration at CaSO4 concentrations between 91 and 2100 mg/ℓ. The effects of CaSO4 on daphnid fecundity could influence the interpretive outcome of industrial wastewater toxicity tests using this species
when the waste and dilution waters contain different concentrations of CaSO4. It is recommended that when performing these tests, dilution water be sampled at the intake site of the industry's water
source, thus assuring initial comparability of the waste and dilution waters. The CaSO4 content of the water prior to and after industrial use should be determined to identify any alterations of CaSO4 concentration during use. Identification of CaSO4 concentration differences can aid in the interpretation of effects associated with the wastewater. 相似文献
46.
C. Lal Kapoor Gerald J. Chader 《Biochemical and biophysical research communications》1984,122(3):1397-1403
A calcium phospholipid-dependent protein kinase (C-kinase) activity was detected in the soluble fraction of rod outer segments (ROS) of the bovine retina. The enzyme required calcium, phosphatidylserine (PS) and diacylglycerol for maximal activity. In the presence of calcium and PS, C-kinase endogenously phosphorylated proteins with molecular weights of 95,000, 91,000, 31,000, 21,000, 19,000, 18,000, 16,000, 14,000 and 11,000. Addition of diolein in the reaction mixture further enhanced the endogenous phosphorylation of these proteins. Retinal was found to inhibit the phosphorylation of endogenous proteins by C-kinase in a concentration dependent manner. Half-maximal inhibition of enzyme activity was obtained at a retinal concentration of about 12μM. These results suggest that calcium, phospholipids and the C-kinase enzyme may play an important role in the functional regulation of rod photoreceptors and, with retinal, perhaps in the visual process as well. 相似文献
47.
Jef D. Boeke Francois La Croute Gerald R. Fink 《Molecular & general genetics : MGG》1984,197(2):345-346
Summary Mutations at the URA3 locus of Saccharomyces cerevisiae can be obtained by a positive selection. Wild-type strains of yeast (or ura3 mutant strains containing a plasmid-borne URA3
+ gene) are unable to grow on medium containing the pyrimidine analog 5-fluoro-orotic acid, whereas ura3
– mutants grow normally. This selection, based on the loss of orotidine-5-phosphate decarboxylase activity seems applicable to a variety of eucaryotic and procaryotic cells. 相似文献
48.
Interspecies conservation of structure of interphotoreceptor retinoid-binding protein. Similarities and differences as adjudged by peptide mapping and N-terminal sequencing. 下载免费PDF全文
Structural properties of the retinal extracellular-matrix glycolipoprotein interphotoreceptor retinoid-binding protein (IRBP) from human, monkey and bovine retinas have been compared. SDS/polyacrylamide-gel-electrophoretic analysis of limited tryptic and Staphylococcus aureus-V8-proteinase digests show virtually identical patterns for the monkey and human proteins, whereas both sets differ considerably from the bovine protein pattern. Time-course digestion shows monkey IRBP to be more readily cleaved than bovine IRBP and also cleaved to smaller fragments. Also, reversed-phase h.p.l.c. of complete tryptic digests of the IRBPs indicate that, although they have in common a similar preponderance of hydrophobic peptides, all three proteins differ extensively in their fine structure. The N-terminal sequences of monkey and bovine IRBPs have been extended beyond those presented in our previous report [Redmond, Wiggert, Robey, Nguyen, Lewis, Lee & Chader (1985) Biochemistry 24, 787-793] to over 30 residues each. The sequences yet show extensive homology, differing at only two positions, although the major monkey sequence has an additional five amino acid residues at its N-terminus ('n + 5' sequence) not observed with bovine IRBP ('n' sequence). The newly determined N-terminal sequence of human IRBP demonstrates the presence of equal amounts of the 'n' and 'n+5' sequences that are qualitatively identical with those of the monkey. The presence of the five-amino-acid-residue extension in primate, but not bovine, IRBP may indicate variation in post-translational processing. 相似文献
49.
Günther Schünzel Gerald Wolf Fritz Rothe Eberhard Seidler 《Cellular and molecular neurobiology》1986,6(1):31-42
Transmitter glutamate/aspartate synthesis is known to proceed along different metabolic pathways. In this light, the functional relevance of glutamate dehydrogenase in postnatally maturing glutamatergic/aspartatergic structures was studied by means of quantitative enzyme histochemistry. The basic requirements concerning the kinetics and calibration of the histochemical glutamate dehydrogenase reaction used were proved to be met in order to obtain valid quantitative data. The histochemically demonstrable activity of glutamate dehydrogenase (EC 1.4.1.3) in the hippocampal formation of the rat increased markedly during postnatal development. On day 30, the distribution pattern observed was similar to that in adult animals. While the enzyme activity rose within cell body layers from day 0 to day 30 by 240-285%, the increase in neuropil layers was found to be up to 830%. Maximum values were seen in the stratum lacunosum-moleculare of CA1 and CA3 and the stratum moleculare of the dentate fascia on day 30. Since the hippocampal neuropil is supposed to be copiously provided with glutamatergic (and aspartatergic?) structures which become functional in rats during the first weeks of postnatal life, the increase in enzyme activity is discussed to be primarily a consequence of maturing synaptic systems using glutamate and/or aspartate as transmitters. 相似文献
50.
Summary We have traced the central projections of the receptor neurons associated with each of the eleven largest taste hairs on the labellum of the blowfly, Phormia regina (Meigen), by staining them with cobaltous lysine. The eleven hairs fall into three groups which reflect their peripheral locations and their branching patterns in the subesophageal ganglion. Group 1, consisting of the anterior hairs (numbers 1 and 2) and Group 3, consisting of the posterior hairs (numbers 9–11) project bilaterally, while Group 2, consisting of the middle hairs (numbers 3–8) projects primarily ipsilaterally. The central projections of the hairs within a single group are similar. Each hair houses four chemoreceptors, which have differing chemical sensitivities and behavioral roles, and one mechanoreceptor. In some cases, there were indications that the different cells within a single hair have different central branching patterns. For some hairs, however, it was clear that a single central branching region and pattern was shared by more than one receptor cell. We failed to find either a continuous somatotopic representation of a hair's position on the periphery, or an anatomical segregation of receptors coding for different modalities. Behavioral experiments indicate that the fly is informed both of the identity of the hair stimulated and of the chemical nature of the stimulus. Our results suggest that this information is not represented on a gross anatomical level. 相似文献