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1.
Over the past year, several significant developments have been made in the field of anion binding. The fundamental principles of molecular recognition are increasingly being better understood, and of particular interest are reports of several synthetic anion receptors able to perform their task in complex natural media. Additionally, macroscopic devices such as anion specific electrodes and membranes based on a molecular recognition approach are now being made. 相似文献
2.
G. Franz M. Reindl S. C. Patel R. Beer I. Unterrichter T. Berger E. Schmutzhard W. Poewe & A. Kampfl 《Journal of neurochemistry》1999,73(4):1615-1625
Increasing evidence suggests that apolipoprotein D (apoD) could play a major role in mediating neuronal degeneration and regeneration in the CNS and the PNS. To investigate further the temporal pattern of apoD expression after experimental traumatic brain injury in the rat, male Sprague-Dawley rats were subjected to unilateral cortical impact injury. The animals were killed and examined for apoD mRNA and protein expression and for immunohistological analysis at intervals from 15 min to 14 days after injury. Increased apoD mRNA and protein levels were seen in the cortex and hippocampus ipsilateral to the injury site from 48 h to 14 days after the trauma. Immunohistological investigation demonstrated a differential pattern of apoD expression in the cortex and hippocampus, respectively: Increased apoD immunoreactivity in glial cells was detected from 2 to 3 days after the injury in cortex and hippocampus. In contrast, increased expression of apoD was seen in cortical and hippocampal neurons at later time points following impact injury. Concurrent histopathological examination using hematoxylin and eosin demonstrated dark, shrunken neurons in the cortex ipsilateral to the injury site. In contrast, no evidence of cell death was observed in the hippocampus ipsilateral to the injury site up to 14 days after the trauma. No evidence of increased apoD mRNA or protein expression or neuronal pathology by hematoxylin and eosin staining was detected in the contralateral cortex and hippocampus. Our results reveal induction of apoD expression in the cortex and hippocampus following traumatic brain injury in the rat. Our data also suggest that increased apoD expression may play an important role in cortical neuronal degeneration after brain injury in vivo. However, increased expression of apoD in the hippocampus may not necessarily be indicative of neuronal death. 相似文献
3.
Methylobacterium rhodesianum MB 126 was cultivated using extended cultures without outflow. The feeding regime was based on the pH-regulated synchronous dosages of ammonia, methanol, phosphatc and trace elements according to supposed stoichiometric relations. The acidity of the culture medium was kept constant at pH 6.8, whereas the dissolved oxygen concentration was adjusted at 80% of saturation by autoregulation of the stirrer speed. However, besides testing technical conditions, two types of fermentations were discovered which are described in this paper. Firstly, although at the beginning of the bioprocesses the impeller speed increased up to 2,000 rpm, a decrease of dissolved oxygen down to zero was unavoidable. Secondly, methanol was accumulated temporarily up to 44 g/l and 26 g/l at 23 h of fermentation time and without inhibition of growth at least up to 30 g/l or PHB production. During this accumulation of the carbon substrate, exponential growth phases were detected showing growth rates of μ = 0.20/h and 0.21/h. But then, phases of retarded growth followed, whereas the methanol disappeared either continuously or after a steady level. In the course of a 54-h fermentation period, the synthesized PHB amounted to a content of above 50% of cell dry mass. From this data, a volumetric productivity of 0.4 g PHB/lxh was estimated. Moreover, the growth related yield coefficients were calculated to YX/MeOH = 0.21 and YX/MeOH = 0.14, whereas the product related yield coefficients amounted to YPHB/MeOH = 0.12 and YPHB/MeOH = 0,09. Since the shift down of growth rates as well as the production of PHB agreed in time with partial oxygen limitation (40% oxygen saturation), the competition observed between the tricarboxylic acid cycle and PHB synthesis was discussed. Summarizing the results, it was concluded that the frequently described inhibitory effect of methanol of above 2 g/l seems to be rather an effect of experimentally chosen conditions than of a general physiological phenomenon. Therefore, it could be demonstrated that the toxicity of methanol could be overcome if it was not dosed at different times but simultaneously with other medium components. 相似文献
4.
Neutrophil association and degradation of normal and acute-phase high-density lipoprotein 3. 总被引:3,自引:0,他引:3
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E G Shephard F C de Beer M C de Beer M S Jeenah G A Coetzee D R van der Westhuyzen 《The Biochemical journal》1987,248(3):919-926
The interaction of normal and acute-phase high-density lipoproteins of the subclass 3 (N-HDL3 and AP-HDL3) with human neutrophils and the accompanying degradation of HDL3 apolipoproteins have been studied in vitro. The chemical composition of normal and acute-phase HDL3 was similar except that serum amyloid A protein (apo-SAA) was a major apolipoprotein in AP-HDL3 (approx. 30% of total apolipoproteins). 125I-labelled AP-HDL3 was degraded 5-10 times faster than 125I-labelled N-HDL3 during incubation with neutrophils or neutrophil-conditioned medium. Apo-SAA, like apolipoprotein A-II (apo-A-II), was more susceptible than apolipoprotein A-I (apo-A-I) to the action of proteases released from the cells. The amounts of cell-associated AP-HDL3 apolipoproteins at saturation were up to 2.8 times greater than N-HDL3 apolipoproteins; while apo-A-I was the major cell-associated apolipoprotein when N-HDL3 was bound, apo-SAA constituted 80% of the apolipoproteins bound in the case of AP-HDL3. The associated intact apo-SAA was mostly surface-bound as it was accessible to the action of exogenous trypsin. alpha 1-Antitrypsin-resistant (alpha 1-AT-resistant) cellular degradation of AP-HDL3 apolipoproteins also occurred; experiments in which pulse-chase labelling was performed or lysosomotropic agents were used indicated that insignificant intracellular degradation occurred which points to the involvement of cell-surface proteases in this degradation. 相似文献
5.
Phosphorus availability under alley cropping and mulched and unmulched sole cropping systems in Costa Rica 总被引:3,自引:0,他引:3
Phosphorus availability was measured in soils under five cropping systems: alley cropping with Erythrina poeppigiana, alley cropping with Gliricidia sepium, sole cropping with Erythrina poeppigiana mulch applied, sole cropping with Gliricidia sepium mulch applied, sole cropping with no mulch. The following parameters were measured: 1) plant-available soil P assessed by P uptake of maize and bean bioassay plants; 2) phosphate desorbable by anion exchange resin; 3) adsorption of added P into isotopically exchangeable and non-exchangeable pools.In the bioassay, P uptake of beans declined in the order: mulched sole-cropped>unmulched sole-cropped>alley-cropped soils. For maize the relative uptake was: mulched sole-cropped>unmulched sole-cropped = alley-cropped soils. These results suggest trees had not incorporated a significant quantity of P into the system after seven years and, probably, there was a decrease in available soil P due to the sequestration of P in the tree biomass. Potentially resin-desorbable P was higher in alley-cropped and mulched sole-cropped soils than in unmulched sole-cropped soils. The adsorption and desorption of added P into and from exchangeable and non-exchangeable pools did not differ between alley-cropped and unmulched sole-cropped soils.Crop yield and crop N, P and K uptake were all higher in the alley crops than in the unmulched sole crop. The supply of P to the crop under alley cropping seems to be dependent on P cycled and released from the mulch. The P cycle in alley cropping appears to be self-sustaining at least under conditions of moderate P fertiliser input. 相似文献
6.
Generation of, lipid neutrophil chemoattractant activity by histamine-stimulated cultured endothelial cells 总被引:3,自引:0,他引:3
H W Farber P F Weller S Rounds D J Beer D M Center 《Journal of immunology (Baltimore, Md. : 1950)》1986,137(9):2918-2924
Endothelial cell-neutrophil interactions are an important aspect of inflammatory responses. Because vascular endothelial cells respond to the inflammatory mediator histamine, these studies determined whether histamine could induce endothelial cells to release substances that affect human neutrophil migration. Cultured bovine and human endothelial cells incubated with histamine released neutrophil chemoattractant activity within 1 min; peak levels were noted in 45 min. Cimetidine, an H2 receptor antagonist, blocked chemoattractant production, whereas diphenhydramine, an H1 receptor antagonist, did not. Cycloheximide did not inhibit release of chemoattractant activity, suggesting de novo protein synthesis was not necessary for its appearance. Extraction with acidified diethyl ether partitioned all neutrophil chemoattractant activity into the organic phase. The lipoxygenase pathway inhibitors, diethylcarbamazine and 5,8,11,14 eicosatetraynoic acid, inhibited generation of this lipophilic chemoattractant activity, whereas indomethacin, a cyclo-oxygenase inhibitor, did not. Resolution of the histamine-induced endothelial cell-derived chemoattractant activity by reverse-phase high pressure liquid chromatography yielded several peaks of chemoattractant activity, none of which co-eluted with leukotriene B4, platelet-activating factor, or two mono-hydroxyeicostetraenoic acids. These findings suggest that endothelial cells release lipid neutrophil chemoattractant activity that may play a role in inflammatory responses associated with histamine. 相似文献
7.
J Karemaker F A Mooi E L de Beer P Schiereck 《Journal of biochemical and biophysical methods》1986,12(1-2):89-99
A microprocessor based digital recording system has been developed to study the fine structure and asymmetry of diffraction spectra from striated muscle during contraction. Two linear 256-element photodiode arrays provide analog videosignals of the diffraction lines imaged onto these charged coupled devices. The photodiode arrays are alternately read and the videosignals can be digitized and stored within 1.36 ms (two images of 256 points) with a spatial resolution of 5 nm. (In this paper the spatial resolution is considered to be the standard deviation of the first-order maximum of a monochromatic wave of the He/Ne laser measured from the diode-arrays, using ideal gratings with a spacing between 1.6 and 3.6 microns.) The system's memory with a capacity of 192 pairs of images of 256 points can be optimized by means of a threshold to contain about 2000 images without any loss of information. A transient recording approach makes the system capable of recording long term slow phenomena of up to 5 s as well as fast events and the combination of fast events within slow processes. The system presented here has a significantly improved time resolution and storage capacity when compared to other systems and is more versatile. This is the first system which enables the simultaneous examination of the fine structure and asymmetry of diffraction spectra. 相似文献
8.
9.
10.
Bioactive recombinant methionyl bovine prolactin: structure-function studies using site-specific mutagenesis 总被引:1,自引:0,他引:1
A method has been developed for the extraction from transformed Escherichia coli cells of methionyl bovine PRL (met-bPRL) in a relatively pure form. While the extracted met-bPRL was as reactive as the native hormone with respect to polyclonal anti-bPRL antibodies, its bioactivity, as measured by the Nb2 lactogen in vitro bioassay, was relatively low. The bioactivity of the met-bPRL could be increased to the same order as that of the native hormone by treatment with a mixture of oxidized and reduced thioredoxin. A number of variant met-bPRLs containing specific amino acid changes have been generated by site-specific mutagenesis. The changes involved the substitution (or deletion) of some of the conserved amino acids in bPRL by the different amino acids present at the corresponding positions in the related, but nonlactogenic bovine GH. Nine mutants containing single amino acid changes had bio- and immunoactivities of the same order as those of met-bPRL. One mutant, which incorporated two of the single amino acid changes (serine 62 to threonine and threonine 65 to alanine), had immunoactivity approximating that of met-bPRL but much lower bioactivity (45%). A further mutant, generated by the deletion of tyrosine 28, had essentially no bioactivity although it could not be distinguished immunologically from met-bPRL or bPRL. The findings are discussed in the light of the putative three-dimensional PRL structure and current hypotheses which seek to relate specific regions of PRL to lactogenic activity. It appears that the first putative alpha-helix of bPRL is important for the binding and mitogenic activity of the hormone. 相似文献