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101.
J M Krueger M L Karnovsky S A Martin J R Pappenheimer J Walter K Biemann 《The Journal of biological chemistry》1984,259(20):12659-12662
The structures of components of the sleep-promoting material purified from human urine were established by fast atom bombardment-mass spectrometry, as reported in the accompanying paper (Martin, S. A., Karnovsky, M. L., Krueger, J. M., Pappenheimer, J. R., and Biemann, K. (1984) J. Biol. Chem. 259, 12652-12658). We report here that two substances isolated from that preparation, viz. N-acetylglucosaminyl-1,6 -anhydro-N-acetylmuramyl-Ala-gamma-Glu-diaminopimelyl-Ala) and that compound lacking the terminal alanine, are active as somnogens. Cerebro-intraventricular administration of 1 pmol of the glycotetrapeptide was sufficient to induce prolonged excess sleep in rabbits. A similar substance obtained from Brevibacterium divaricatum in which the free carboxyls of the glutamic and diaminopimelic moieties, indicated above, were amidated (N-acetylglucosaminyl-1,6-anhydro-N-anhydromura-myl-Ala-iso- Gln- epsilon-amido-diaminopimelyl -Ala-Ala) was not active as a promoter of slow-wave sleep. Deamidation of this peptide to a mixture of the free dicarboxylic forms produced a somnogenic substance. Our findings show that in addition to the muramyl form of peptidoglycan monomers, the anhydro muramyl form, with no reducing end, is compatible with somnogenic activity. Furthermore, the data obtained with a natural product amplify our earlier observations with smaller synthetic molecules of the importance of amidation/deamidation in the structure-activity relationships of muramyl peptides. 相似文献
102.
103.
104.
Ascites from patients with metastatic ovarian carcinoma contains high amounts of an activity that increases vascular permeability, as easily detected by a rat skin test. Ascites was fractionated by gel permeation and reversed-phase high-performance liquid chromatographies. The fractions were analysed for permeability-increasing activity. In this way a peptide was isolated and identified as Ile-Ser-bradykinin by sequence and amino-acid analyses. It is identical with T-kinin which has previously been detected as a product of an acute-phase protein, T-kininogen, in rats but never in human material. The so far identified human kininogens, i.e. high- and low-molecular mass kininogens, can only release Met-Lys-bradykinin or its degradations products, as Ile-Ser-bradykinin is not a part of their structure. However, the present results provide evidence that the permeability factor Ile-Ser-bradykinin under certain conditions can be produced in considerable amounts also by human tissues. 相似文献
105.
Walter Pflumm 《Ethology : formerly Zeitschrift fur Tierpsychologie》1986,72(1):15-21
The rate of supply of sucrose solution at an artificial food source was varied by means of a pump, while the concentration of the solution and the temperature at the food source were kept constant. The behaviour of the collector wasps was found to change in correlation with the supply rate, in several respects. As rate of supply increases
- a) the duration of sojourn at the food source decreases;
- b) the volume of solution removed per h increases;
- c) the number of single visits during a sojourn and per h decreases;
- d) the duration of single visits increases, except that at extremely high supply rates the single visits become shorter.
106.
Robert W. Lovitt Robert P. Walter J. Gareth Morris Douglas B. Kell 《Applied microbiology and biotechnology》1986,23(3-4):168-173
Summary The problem of obtaining a rapid estimate of the microbial content of an immobilised cell suspension is addressed. The low-frequency conductivity of free-living cell suspensions of Clostridium pasteurianum is lower than that of the medium in which they are suspended, by an amount conforming to the Bruggeman relation. The conductivity of the cell wall makes a negligible contribution to the measured conductivity under the conditions used. Calcium alginate beads (lacking microbial cells) lower the conductivity of a solution with which they have been equilibrated by an extent which is a function of the concentration of alginate gel used in forming the beads. When this is taken into account, the ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present. 相似文献
107.
Gary Rose Walter Heiligenberg 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1986,158(5):613-624
Eigenmannia is able to discriminate the sign of the difference, Df, between the frequency of a neighbor's electric organ discharge (EOD) and that of its own EOD. This discrimination can be demonstrated at the level of individual neurons of the midbrain. Intracellular and extracellular recordings of such sign-selective cells revealed the following: Units preferring positive Dfs and units preferring negative Dfs were found with equal frequency. The degree of selectivity was also similar for these two classes of neurons. All sign-selective units were sensitive to the magnitude of the frequency difference, i.e. the beat rate. Most units responded best to beat rates in the 4-8 Hz range. Sign-selectivity was observed only when the jamming signal (S2) was presented through electrodes other than those used to deliver the mimic (S1) of the fish's EOD, i.e. only when amplitude modulations were accompanied by modulations of differential phase. Intracellular studies suggest that most sign-selective neurons of the tectum are large, multipolar cells in the stratum album centrale. These cells send projections to the reticular formation, to lamina 9 of the torus semicircularis and to the N. electrosensorius. 相似文献
108.
Walter W. McAlhaney Naren L. Banik Seymour Greenfield Edward L. Hogan 《Neurochemical research》1986,11(2):173-183
Six proteolytic enzymes were assayed for activity in quaking CNS in examining the hypothesis that increased proteolytic activity contributes to the hypomyelination characteristic of this mutant. Cathepsin B-like enzyme, cathepsin D, neutral proteinase, calcium-activated neutral proteinase, prolyl endopeptidase, and diaminopeptidase II were assayed in whole homogenate of brain or spinal cord and each was found to have activity similar to that in normal mice. These results do not support a relationship between proteolysis and the genetic defect and suggest that other factors should be investigated to delineate the pathogenesis of this mutant. 相似文献
109.
Sea urchins have elaborated multiple defenses to assure monospermic fertilization. In this work, we have concentrated on a study of the mechanism(s) by which hydrogen peroxide (H2O2) prevents polyspermy in Arbacia punctulata. We found that it is not H2O2 but probably hypochlorous acid/hypochlorite (HOCl/OCl?) derived from H2O2 that is toxic to the supernumerary sperm. The spermicidal activity of H2O2 is potentiated by at least one order of magnitude by cupric ions (Cu2+). This increased toxicity is not due to the formation of hydroxyl radicals (·OH) because ·OH scavengers did not counteract the activity of Cu2+. More-over, substitution of Cu2+ by ferrous ions (Fe2+), which are known to cause formation of ·OH from H2O2, had no effect on fertilization even at 102?103 times higher concentrations. In contrast, 3-amino-1,2,4-triazole (AT), an HOCl/OCl? scavenger, totally reversed the toxic effects of Cu2+. Furthermore, we found that HOCl/OCl? is generated in solutions of H2O2 and Cu2+ in the presence of 0.5 M NaCl and that its accumulation is abolished by AT. Thus it is possible that the antifertility properties of copper are due to its ability to mediate formation of HOCl/OCl?. HOCl/OCl? generated by Cu2+ from H2O2 and Cl?, a low concentration of exogenously added HOCl/OCl?, or increased concentrations of H2O2 has similar inhibitory effects on the fertilization process in sea urchins. Therefore, we suggest that polyspermy is prevented by the action of a myeloperoxidase that affects the formation of HOCl/OCl? from the Cl? present in sea water through reaction with H2O2 generated by the newly fertilized egg. 相似文献
110.
So that valuable products from the neem tree (Azadirachta indica) will be readily available in the future, countries in the neotropics should emulate Haiti and grow the species where it thrives even in eroded, semiarid, depauperate areas suitable for few other trees. 相似文献