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51.
R Brown Z Li C Y Vriend R Nirula L Janz J Falk D M Nance D G Dyck A H Greenberg 《Cellular immunology》1991,132(1):84-93
Intracerebroventricular (ICV) injections of interleukin-1 beta (IL-1 beta) produced a dose-dependent increase in plasma corticosterone and adrenocorticotropic hormone (ACTH) within 2 hr of injection and then declined over the next 24 hr. Using a potent steroidogenic dose of IL-1 beta (5 ng), ICV injection resulted in suppression of splenic macrophage IL-1 secretion following stimulation by LPS in vitro. Macrophage TGF-beta secretion was not affected, indicating a differential action of ICV IL-1 beta on macrophage cytokine production. Following adrenalectomy (ADX), the suppressive effect of ICV IL-1 beta was reversed and resulted in stimulation of macrophage IL-1 secretion, indicating that the suppression was mediated by adrenocorticol activation. However, surgical interruption of the splenic nerve to eliminate autonomic innervation of the spleen also prevented the macrophage suppressive signal in rats given ICV IL-1 beta. Furthermore, the combination of ADX and splenic nerve section resulted in a potent stimulatory effect of ICV IL-1 beta on splenic macrophage IL-1 secretion which was greater than either ADX or splenic nerve section alone. These results support the concept of a negative feedback on macrophage IL-1 secretion by the central action of IL-1 beta and indicate that both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system mediate this effect. 相似文献
52.
Recovery from 60 min of photoinhibitory treatment at photosynthetic photon flux densities of 500, 1400 and 2200 μMmol m?2 s? was followed in cells of the green alga Chlamydomonas reinhardtii grown at 125 μMmol m?2 s?1. These light treatments represent photoregulation, moderate photoinhibition and strong photoinhibition, respectively. Treatment in photoregulatory light resulted in an increased maximal rate of oxygen evolution (Pmax) and an increased quantum yield (Φ), but a 15% decrease in Fv/FM. Treatment at moderately photoinhibitory light resulted in a 30% decrease in Fv/FM and an approximately equal decrease in Φ. Recovery in dim light restored Fv/FM within 15 and 45 min after high light treatment at 500 and 1400 μMmol m?2 s?1, respectively. Convexity (Θ), a measure of the extent of co-limitation between PS II turnover and whole-chain electron transport, and Φ approached, but did not reach the control level during recovery after exposure to 1400 μMmol m?2 s?1, whereas Pmax increased above the control. Treatment at 2200 μMmol m?2 s?1 resulted in a strong reduction of the modeled parameters Φ, Θ and Pmax. Subsequent recovery was initially rapid but the rate decreased, and a complete recovery was not reached within 120 min. Based on the results, it is hypothesized that exposure to high light results in two phenomena. The first, expressed at all three light intensities, involves redistribution within the different aspects of PS II heterogeneity rather than a photoinhibitory destruction of PS II reaction centers. The second, most strongly expressed at 2200 μmol m?2 s?1, is a physical damage to PS II shown as an almost total loss of PS IIα and PS II QB-reducing centers. Thus recovery displayed two phase, the first was rapid and the only visible phase in algae exposed to 500 and 1400 μmol m?2 s?1. The second phase was slow and visible only in the later part of recovery in cells exposed to 2200 μmol m?2 s?1. 相似文献
53.
Tissue-specific and developmental regulation of rod opsin chimeric genes in transgenic mice. 总被引:13,自引:0,他引:13
Chimeric gene fusions between 4.4 kb of rod opsin 5' flanking sequence fused to a diphtheria toxin gene and 4.4 kb or 500 bp of rod opsin 5' flanking sequence fused to the E. coli IacZ gene were used to generate transgenic mice for analysis of cell type-specific expression and temporal and spatial distribution of reporter gene product during retinal development. Opsin-diphtheria toxin transgene expression evoked photoreceptor-specific cell death. The 4.4 kb opsin-IacZ transgene followed temporal and spatial gradients of expression that approximate opsin expression. The 500 bp opsin fragment targeted expression to photoreceptors, but expression was weaker and nonuniform, suggesting that elements located upstream may be required for enhanced and uniform spatial expression. 相似文献
54.
Determination of 4-hydroxyproline in collagen by gas chromatography/mass spectrometry 总被引:2,自引:0,他引:2
Edward E. Tredget Norine Falk Paul G. Scott Alan M. Hogg John F. Burke 《Analytical biochemistry》1990,190(2):259-265
Derivatization of 4-hydroxyproline (Hyp) in collagen using trifluoroacetylation and methanol esterification produces two derivatives when analyzed by gas chromatography/mass spectrometry (GC/MS). The diacyl derivative N,O-bis(trifluoroacetyl)-4-hydroxy-L-proline methyl ester (N,O-TFA-Hyp) formed in this manner has a shorter retention time and different fragmentation pattern by GC/MS as compared to the slower eluting monoacetylated species N-trifluoroacetyl-4-hydroxy-L-proline methyl ester (N-TFA-Hyp). By selected ion monitoring of the appropriate ions of either N,O-TFA-Hyp (m/z 164, 278) or N-TFA-Hyp (m/z 164, 182) efficient quantitation of Hyp in collagen is possible within the broad range of 5-1000 ng with a lower limit of detection of 0.5 ng per injection. Measurement of 18O2 incorporation into collagen is possible by selected ion monitoring of the m/z 182 ion formed only from the monoacetylated derivative, N-TFA-Hyp, produced by methanol solvolysis of the N,O-TFA-Hyp derivative, as proposed herein. 相似文献
55.
We have studied the changes in the activities of both nitrogenase (switch off) and glutamine synthetase in Rhodospirillum rubrum upon addition of ammonium ions or glutamine to nitrogen fixing cultures. Both activities decrease drastically and return in a parallel manner when added ammonia is metabolized. The decrease in glutamine synthetase activity does not seem to be primarily due to adenylylation of the enzyme. Addition of glutamine to cells starved for nitrogen results in inactivation of glutamine synthetase but nitrogenase is only partially switched off.Abbreviations CeMe3NBr
Cetyltrimethylammonium bromide
- Hepes
N-2-hydroxyethyl-piperazine-N-2 sulfonic acid
- MSO
methionine-D,L-sulfoximine
- Tea-Dmg
triethanol amine-3,3-dimethylglutaric acid 相似文献
56.
1. The effects of perchlorate on cytochrome c have been investigated by 1H and 35Cl NMR, electron paramagnetic resonance and optical spectroscopy. 2. The pK values for the formation and disappearance of the major alkaline conformation were found to be displaced from 9.3 to 8.3 and from 10.4 to 10.9, respectively. The displacement was dependent on the ClO4(-) concentration below 0.1 M. 3. Competition experiments between perchlorate and chloride show that ClO4(-) binds both to the neutral and alkaline forms but with a higher affinity for the latter. The appearance of a new binding site in the alkaline form accounts for the markedly enhanced relaxation rate of 35ClO4(-) in this pH range. Complex formation between cyanide and the alkaline species results in the loss of this binding site, which probably is located close to or within the heme crevice. 4. The neutral form of ferricytochrome c also binds perchlorate strongly as evidence by the unique appearance of a high-spin signal dependent on pH and perchlorate concentration. This signal disappears with the same pK value as the neutral form. The effects of perchlorate on cytochrome c are due to specific binding of this ion. 相似文献
57.
58.
D Falk 《Acta anatomica》1978,101(4):334-339
A photogrammetric computer analysis of 88 endocasts, representing 8 genera of Old World monkeys, reveals cortical asymmetry in lengths of the Sylvian fissure, superior temporal sulcus, lateral edge of the orbit and distance separating rectus and arcuate sulci. Hypothetical expansion of left prefrontal and parietal integration cortices explains these asymmetries. 相似文献
59.
Heinz Falk 《Planta》1976,128(1):15-22
Summary The fine structure of chromoplasts in epidermal cells of flower petals of Tropaeolum has been investigated by light, polarizing, and electron microscopy at different stages of development. The pale greenish-yellow petals still enclosed in the bud contain barely differentiated chloroplasts with few, irregular grana. The chromoplasts of unfolding petals show differently oriented bundles of tubules with variable diameters (mean: 17 nm). Thylakoid membranes become reduced more and more. The tubular bundles are intermingled with numerous isodiametric bodies of ca. 50 nm diameter; these bodies are better discernible at later stages when the chromoplasts possess a less dense matrix. The chromoplasts of open flowers are in a state of disorganization at a time when the cytoplasm still appears normal. A comparison is made between chromoplast tubules and tubular structures described from other kinds of plastids. The observations are discussed in view of chromoplast typology and with regard to possible processes underlying chromoplast differentiation in flowers.Abbreviations in Figures Chr
chromoplast
- CT
chromoplast tubules
- Cy
cytoplasm
- D
dictyosome
- IB
isodiametric body
- M
mitochondrion
- MT
microtubule
- oG
osmiophilic globule
- S
S-body
- St
starch grain
- V
vacuole
All micrographs from glutaraldehyde-OsO4-fixed material, unless otherwise specified. The bar designates 1 m (multiples or fractions of it indicated). 相似文献
60.
Various 8 alpha-sulfur-linked peptides related to the flavinyl peptides isolated from mitochondrial monoamine oxidase were synthesized in high yield and purity. The peptides, protected by an acetyl-blocking group on the amino terminus, were synthesized by conventional liquid-phase techniques and coupled to a tetraacetylriboflavin derivative activated in the 8alpha position. In some cases, the ribityl side chains of the flavinyl peptides were selectively deacetylated. In other cases, the thioether functions were oxidized to form sulfones. These flavinyl peptides were studied by uv-visible absorption and circular dichroic spectroscopies. A close correspondence in spectroscopic and other chemical properties indicated the identity of the synthetic and naturally obtained flavinyl peptides. Differences between the tetraacetylriboflavinyl and riboflavinyl peptides indicate an interaction between the ribityl side chain and thioether function in aqueous media. Evidence was obtained for an intramolecular complex between the tyrosyl and isoalloxazine moieties in aqueous media. Substitution in the 8alpha position was accompanied by an impairment of the protonation of the N1 position of the isoalloxazine ring and a lowering of the redox potential relative to the parent 8-methyflavins. 相似文献