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41.
Dr. P. Gil-Loyzaga R. Pujol R. Mollicone A.-M. Dalix R. Oriol 《Cell and tissue research》1989,257(1):17-21
Summary The presence of human blood-group antigens was analyzed in the rat cochlea during its postnatal development, using anti-A, anti-B and anti-H antibodies. At no stage was reactivity with anti-A antibody observed. With the anti-H antibody, a strong reactivity was observed from 1 to 9 days after birth within hair cells and some other surface epithelial cells of the cochlear duct. After postnatal day 9, only a faint reactivity persisted in a few non-sensory cells. With the anti-B antibody, only hair cells were selectively labeled. At early stages (postnatal day 1 and 3), the reactivity was intense and observed both around the cell surface and within the supranuclear region of cytoplasm. Later on, the reactivity decreased; it was limited at postnatal day 9 to a reactive spot below the cuticular plate. Results are compared with a preliminary finding describing the first appearance of B and H antigens in the organ of Corti at a prenatal stage, and with data concerning other sensory and neural structures. The appearance and progressive disappearance of B and H antigens on sensory and non-sensory cells can be correlated with significant events in the development of the cochlea. The transient expression of B and H antigens in cochlear sensory cells may correspond to developmental changes in their surface glycoconjugates. 相似文献
42.
Jan Holgersson Michael E Breimer Anita Jacobsson Lola Svensson Ami Ulfvin Bo E Samuelsson 《Glycoconjugate journal》1990,7(6):601-608
Total non-acid glycolipid fractions and total sodium dodecylsulphate (SDS) solubilized protein fractions were isolated from human thrombocytes obtained from single human donors having different blood group A1/A2 phenotypes. The blood group A glycolipid antigens were characterized by immunostaining of thin layer plates with different monoclonal anti-A antibodies. The glycoproteins carrying blood group A epitopes were identified by SDS-PAGE and Western blot analysis using a monoclonal anti-A antibody. Blood group A glycolipid antigens were found in both A1 and A2 thrombocytes but the A2 individuals expressed at least ten times less A glycolipids compared to the A1 individuals. Expression of A type 3/4 chain and small amounts of A type 1 chain glycolipids were seen in thrombocytes of both A1 and A2 individuals, while the type 2 chain A glycolipids appeared to be missing from the A2 thrombocytes. Blood group A reactive glycoproteins were only found in thrombocytes of A1 individuals and could not be detected in A2 individuals or a blood group O individual. The major blood group A glycoprotein were found as a double band migrating in the 130 kDa region.Abbreviations SDS
sodium dodecyl sulfate
- PAGE
polyacrylamide gel electrophoresis
- HPTLC
high performance thin layer chromatography
- CBB
Coomassie brilliant blue
- GVH
graft versus host
Part of this work was presented at the Xth International Symposium on Glycoconjugates, Jerusalem, Israel. September, 1989.In the short hand designation for glycolipids, the letter indicate blood group determinant, the first numeral, the number of sugar residues, and the second numeral, the type of carbohydrate chain. Thus, A-6-1 means a hexaglycosylceramide with a blood group A determinant based on the type 1 carbohydrate chain. 相似文献
43.
Opacity factor from group A streptococci is an apoproteinase 总被引:7,自引:0,他引:7
Opacity factor (OF) is an enzyme, elaborated by certain serotypes of group A streptococci, which produces opalescence in mammalian sera. OF has been designated a lipoproteinase. Lipoproteins are complex structures and many enzymes are involved in their catalysis. We therefore set out to establish which of the many enzymes OF could be. Results showed that OF rendered high density lipoprotein (HDL) insoluble, accounting for the opalescence in serum, and altered its electrophoretic mobility. Electron microscopy revealed that OF caused an aggregation of HDL and an alteration in molecule shape. OF specifically split apoprotein AI of HDL into two fragments demonstrable by SDS-PAGE. We therefore designate OF as an apoproteinase. 相似文献
44.
Frank Arnal Lucien J. Coté Sara Ginsburg Glen D. Lawrence Ali Naini Mary Sano 《Neurochemical research》1990,15(6):587-591
We have synthesized the tertiary amines of pyridostigmine and neostigmine, 3-pyridinol dimethylcarbamate (norpyridostigmine) and 3-dimethylaminophenol dimethylcarbamate (norneostigmine) respectively, and we have tested their abilities to cross the blood-brain barrier and inhibit mouse brainAChE activity. The in vivo inhibition of AChE activity by norpyridostigmine reaches 72% at 10 minutes which is comparable to that seen with physostigmine (73% at 10 minutes). Inhibition by norneostigmine is less effective (50% at 10 minutes) and approaches that obtained with tetrahydroaminoacridine (57% at 10 minutes). These data show that both norpyridostigmine and norneostigmine cross the blood-brain barrier and that they are effective inhibitors of mouse brain AChE activity. These drugs could be useful in the treatment of memory, impairment associated with Alzheimer's disease, and other memory disorders. 相似文献
45.
Bacterial interactions with silver 总被引:5,自引:0,他引:5
Summary This review examines interactions between bacteria and the biologically non-essential metal, silver. Aspects of silver toxicity, tolerance and accumulation (possible binding and uptake as opposed to energy-dependent transport) in bacteria are discussed. In addition, plasmid biology is examined briefly since little information is available on the exact mechanism(s) of plasmid-endoced silver resistance in bacteria. 相似文献
46.
J.-J. Bonnet S. Benmansour J.-M. Vaugeois J. Costentin 《Journal of neurochemistry》1988,50(3):759-765
At 0°C, when Na+ was the only cation present in the incubation medium, increasing the Na+ concentration from 3 to 10 mM enhanced the affinity of [3H]l-[2-(di-phenylmethoxy)ethyl]-4-(3-phenyl-2-propenyl)piperazine ([3H]GBR 12783) for the specific binding site present in rat striatal membranes without affecting the 5max. For higher Na+ concentrations, specific binding values plateaued and then slightly decreased at 130 mM Na+. In a 10 mM Na+ medium, the KD and the Bmax were, respectively, 0.23 nM and 12.9 pmol/mg of protein. In the presence of 0.4 nM [3H]GBR 12783, the half-maximal specific binding occurred at 5 mM Na+. A similar Na+ dependence was observed at 20°C. Scatchard plots indicated that K+, Ca2+, Mg2+, and Tris+ acted like competitive inhibitors of the specific binding of [3H]GBR 12783. The inhibitory potency of various cations (K+, Ca2+, Mg2+, Tris+, Li+ and choline) was enhanced when the Na+ concentration was decreased from 130 to 10 mM. In a 10 mM Na+ medium, the rank order of inhibitory potency was Ca2+ (0.13 mM) > Mg2+ > Tris+ > K+ (15 mM). The requirement for Na+ was rather specific, because none of the other cations acted as a substitute for Na+. No anionic requirement was found: Cl-, Br-, and F- were equipotent. These results suggest that low Na+ concentrations are required for maximal binding; higher Na+ concentrations protect the specific binding site against the inhibitory effect of other cations. 相似文献
47.
Inhibition by Cyclic AMP of Phorbol Ester-Potentiated Norepinephrine Release from Guinea Pig Brain Cortical Synaptosomes 总被引:8,自引:4,他引:4
Hisato Shuntoh Kohtaro Taniyama Hisashi Fukuzaki Chikako Tanaka 《Journal of neurochemistry》1988,51(5):1565-1572
The involvement of Ca2+/phospholipid-dependent protein kinase (protein kinase C, PKC) and cyclic AMP-dependent protein kinase in the K+-evoked release of norepinephrine (NE) was studied using guinea pig brain cortical synaptosomes preloaded with [3H]NE. 12-O-Tetradecanoylphorbol-13-acetate (TPA), a potent activator of PKC, enhanced the K+-evoked release of [3H]NE, in a concentration-dependent manner, but with no effect on the spontaneous outflow and uptake of [3H]NE in the synaptosomes. The apparent affinity of the evoked release for added calcium but not the maximally evoked release was increased by TPA (10(-7) M). Inhibitors of PKC, polymyxin B, and a more potent inhibitor, staurosporine, counteracted the TPA-induced potentiation of the evoked release. Both forskolin and dibutyryl cyclic AMP (DBcAMP) enhanced the evoked release, but reduced the TPA-potentiated NE release. A novel inhibitor of cyclic AMP-dependent protein kinase, KT5720, blocked both the forskolin-induced increase in the evoked release and its inhibition of TPA-induced potentiation in the evoked release, thereby suggesting that forskolin or DBcAMP counteracts the Ca2+-dependent release of NE by activating cyclic AMP-dependent protein kinase. These results suggest that the activation of PKC potentiates the evoked release of NE and that the activation of cyclic AMP-dependent protein kinase acts negatively on the PKC-activated exocytotic neurotransmitter release process in brain synaptosomes of the guinea pig. 相似文献
48.
Peter Tompa 《Journal of molecular evolution》1988,27(2):147-153
Summary Of the 20 protein amino acids, 16 have a methylene group at the position, and a further three bear a methine group. No aromatic, carboxamido, carboxylic carbon, or hetero atoms are attached directly to the carbon, but they are separated by this methylene or occasionally by a longern-alkylene spacer group. Therefore, the structure of the protein amino acids should rather be formulated as H2N–CH((CH2)n–R)–COOH instead of the generally accepted H2N–CH(R)–COOH. The appearance of and the role played by the spacer group are discussed in an evolutionary context. It is suggested that the spacer group appeared as a result of prebiotic selection, based on the relative abundance, racemization rate, and suitability for thermal polymerization of the protein amino acids and their homologs with various spacer group lengths. At the biotic level of evolution the requirements for ribosomal polymerization, as well as the abilities of polypeptides to maintain a stable and flexible threedimensional structure and to bind ligands are considered and are proposed to have been responsible for the possible exclusion of longer spacer groups. It is concluded that the general role of the spacer group is to ensure the uniformity of the constant regions H2N–CH(-)–COOH and the individuality of the R contact groups by spatially separating them. 相似文献
49.
Water culture, growth chamber, greenhouse and field experiments were conducted to compare the effect of NH4−N and NO3−N on yield and N uptake of rapeseed (Brassica campestris L.). In water culture, the yields of 28-day old rapeseed plants grown at 14 μg N ml−1 were double with NO3 compared to NH4, but N uptake was little affected. There was no such effect when concentration was reduced to 3.5 or 7 μg N ml−1. The yield and N uptake of 26-day old rapeseed grown on six soils (pH 4.6 to 6.5) in pots in a growth chamber were much greater
with NO3 than with NH4, although N concentration was more in the NH4- than the NO3-grown plants. In a greenhouse experiment with rapeseed grown on 12 potted soils, the N uptake of applied N was greater with
NO3 than with NH4 on all soils. Averages were 63% with NH4 and 78% with NO3. However, NH4-fixation capacities of the soils were only weakly correlated with yield from the two sources of N (r=0.48) and the relation
was similar with N uptake. In contrast to the behavior of water culture, growth chamber and greenhouse experiments, the 33
field experiments did not show consistent difference in seed yield with NH4 and NO3 applied at time of seeding. In nine field experiments where band application was used for Ca(NO3)2, (NH4)2 SO4, NH4 NO3, yield tended to be greatest for (NH4)2SO4. However, in 19 experiments on acid soils with and without lime, yields in most cases were similar with (NH4)2SO4 and NH4 NO3. Nitrification inhibitors were added to spring banded NH4-based fertilizers in five experiments, but the yields were not influenced.
Scientific Paper No. 558, Lacombe Research Station, Agriculture Canada. 相似文献
50.
Laboratory incubation and field experiments were conducted to evaluate thiourea, ATC (4-amino-1, 2, 4 triazole hydrochloride)
and N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) as inhibitors of nitrification of fertilizer N. In the incubation experiment,
most of the added aqueous NH3 or urea was nitrified at 14 days on both soils, but addition of the inhibitors to fertilizer N decreased the conversion of
NH4−N to NO3−N markedly. There was less nitrification for ATC and thiourea but not for N-Serve 24 E when the fertilizers and the inhibitors
were placed at a point as opposed to when mixed into soil. After 28 days, ATC and N-Serve 24 E were more effective in inhibiting
nitrification than thiourea. ATC and N-Serve 24 E also inhibited release of mineral N (NH4−N+NO3−N) from native soil N. In the uncropped field experiment, which received N fertilizers in the fall, nitrification of fall-applied
N placed in the 15-cm bands was almost complete by early May in the Malmo soil, but not in the Breton soil. When ATC or thiourea
had been applied with urea, nitrification of fall-applied N was depressed by May and the recovery of applied N as NH4−N was greater with increasing band spacing to 60 cm or placing N fertilizer in nests (a method of application where urea
prills were placed at a point in the soil in the center of 60×60 cm area). In late June, the percentage recovery of fall-applied
N in soil as NH4−N or mineral N increased with wide band spacing, or nest placement, or by adding ATC to fertilizer N on both soils. These
results indicate that placing ammonium-based N fertilizers in widely-spaced bands or in nests with low rates of inhibitors
slows nitrification enough to prevent much of the losses from fall-applied N.
Scientific Paper No. 552, Lacombe Research Station, Research Branch, Agric, Can. 相似文献