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Abstract: [3 H]Strychnine specifically binds to membrane fractions isolated from rat retinae. The binding is saturable, with an apparent dissociation constant, K D , of 14.3 × 10−9 M and 205 fmol bound/mg protein. Specific binding is time-dependent and proportional to protein concentration. Glycine and taurine are equally potent inhibitors of [3 H]strychnine binding ( K i = 4 × 10−5 M); no other amino acids endogenously present in the retina inhibited [3 H]strychnine binding. 相似文献
74.
Adenosine and guanosine uptake have been studied in the rat retina. Both nucleosides are taken up in a time- and temperature-dependent manner by dispersed rat retinal cells. The uptake of both nucleosides is Na+-dependent and Ca++-independent. Initial rate studies of guanosine and adenosine uptake demonstrate a single uptake process for each nucleoside with KD values of 2.1 and 2.9 uM, and maximal rates of 24 and 17 pmol/mg protein/min, respectively. Guanosine uptake was inhibited by adenosine with a KI of 12.1 uM whereas guanosine inhibited adenosine uptake with a KI value greater than 10?3 M. LN6-phenylisopropyladenosine, a nucleoside analog, was the most potent inhibitor of adenosine and guanosine uptake with KI values of 25 and 8 uM, respectively. Phosphodiesterase inhibitors (isobutylmethylxanthine and theophylline) and biogenic amines (dopamine, norepinephrine, and histamine) had no significant effect on the uptake of guanosine or adenosine at concentrations up to 100 uM. 相似文献
75.
The impact of an industrially contaminated lake on heavy metal levels in its effluent stream 总被引:2,自引:1,他引:1
Levels of cadmium and zinc in various components of Williamson Ditch (an industrially contaminated stream flowing into Palestine Lake), Trimble Creek (a stream draining Palestine Lake) and the Tippecance River (a river receiving Trimble Creek) were determined. Water, sediment, plant, fish and clam samples were analyzed for cadmium and zinc content by atomic absorption spectrophotometry. Unweighted mean metal concentrations in Trimble Creek were the following: water, 51 µg Zn/1 and 4.2 µg Cd/1; sediment, 592 µg Zn/g and 48.8,µg Cd/g; plants, 375 µm Zn/g and 7.91 µg Cd/g; fish, 145 µg Zn/g and 6.02 µg Cd/g. These concentrations were generally lower than those found in Williamson Ditch and higher than those found in the Tippecanoe River or background levels previously reported for other aquatic ecosystems. 相似文献
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"Generalized distances" between centromeres were statistically analyzed (chi2 test) on 50 normal female trypsin-banded metaphase figures. This study revealed that the homologous chromosomes of the pairs 13, 17, 14, and 21 lie closer together than would be expected by a reference distribution, and this in a statistically significant way. The same relative position was demonstrated for the chromosome groups 13-14, 13-21, 14-21, 15-22, and 14-22. Evidences were collected that also showed that homologous chromosomes of the pairs 1, 19, and 20 and the chromosome groups 15-21, 13-15, and 18-20 tend to lie closer together. Giving a functional interpretation to the phenomenon of non-random distribution of chromosomes in metaphase figures, it may be suggested that the chromosomes 13, 14, and 21 are involved in the organization of the human nucleolar organizers, more frequently than the other D- and G-group chromosomes. 相似文献
78.
The distribution of non-covalently bound secretory component (SC) on the two subclasses, IgA-f and IgA-g of rabbit secretory IgA (sIgA) was determined; the two subclasses were separated from each other by the use of antibody-immunosorbent columns and were subjected to SDS polyacrylamide gel electrophoresis. No SC appeared to be dissociated from the IgA-f molecules from each of 11 different rabbits; the IgA-g molecules, however, did have SC which was dissociated by SDS. Thus, all of the noncovalently bound SC on rabbit sIgA resides on the IgA-g subclass molecules. 相似文献
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