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1.
In the frog intestine, both in vitro and in vivo, experiments were carried out in order to increase knowledge of the mechanism of sugar exit across the basolateral membrane of the enterocyte. The frog intestine was chosen because it lacks crypt cells and, consequently, any external fluid circuit mechanism during sugar transport can be avoided. Therefore, the sugar concentration in the absorbate collected on the serosal side is likely to be similar to that present underneath the basolateral membrane of the enterocyte. Under this condition, cell and absorbate sugar concentrations are similar; yet there is a concomitant net transintestinal sugar transport. Moreover, in in vivo experiments a net transintestinal sugar transport takes place even against a concentration difference. These results suggest that sugar exit across the basolateral membrane is not simply due to a chemically facilitated diffusion. 相似文献
2.
A 1H NMR study of the peptide alamethicin, which forms voltage-gated ion channels in membranes, is described. The molecule was studied in methanol as a function of temperature and pH. A complete assignment of the spectra is given, including several stereospecific assignments. Alamethicin was found to have a structure substantially similar to the crystal although, in solution, the C-terminal dipeptide adopts a somewhat extended conformation. The overall conformation was insensitive to the ionization of the side chain of the only ionizable group, Glu-18. 相似文献
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M Fekadu J H Shaddock J W Sumner D W Sanderlin J C Knight J J Esposito G M Baer 《Journal of wildlife diseases》1991,27(4):681-684
Twenty nine skunks (Mephitis mephitis) were vaccinated orally with raccoon poxvirus (RCN) recombinants: 10 with a recombinant expressing the rabies virus glycoprotein (RCNRG), 10 with RCNRG mixed with a recombinant expressing the rabies virus nucleoprotein (RCNRN) and nine with RCN alone. Rabies virus neutralizing antibodies were detected in six of the 20 skunks; five skunks (three given RCNRG, two given a mixture of recombinants) survived a rabies challenge that was lethal for nine skunks vaccinated with RCN alone. 相似文献
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Substance P as a transglutaminase substrate: identification of the reaction products by fast atom bombardment mass spectrometry 总被引:1,自引:0,他引:1
R Porta C Esposito S Metafora P Pucci A Malorni G Marino 《Analytical biochemistry》1988,172(2):499-503
Substance P was found to be an effective acyl donor substrate of transglutaminase in vitro, the reaction products having been examined by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fast atom bombardment mass spectrometry. Electrophoretic experiments showed that Substance P incorporated 14C-labeled polyamines when incubated with purified guinea pig liver transglutaminase and Ca2+. Extensive use of fast atom bombardment mass spectrometry allowed to establish that: i) a 1:1 adduct Substance P-spermine is formed; ii) only a single glutamine residue out of two, i.e. Gln-5, acts as acyl donor, iii) the single lysine residue of the neuropeptide is unable to act as acyl acceptor. A direct analytical methodology to detect transglutaminase reaction products is described. 相似文献
7.
A Faelli M Tosco M N Orsenigo G Esposito V Capraro 《Archives internationales de physiologie et de biochimie》1983,91(5):423-432
Basolateral membranes from rat jejunal enterocytes have been obtained by self-orienting Percoll-gradient centrifugation. Bicarbonate and L-glucose uptake into osmotically active basolateral membrane vesicles has been studied by a rapid filtration technique. In closed vessels and at pH 8.2 the uptake kinetics of both [14C]bicarbonate and L[3H]glucose have been followed for 30 min at 18 degrees C. Bicarbonate uptake seems to be fast and in efflux experiments SITS and DIDS effect is negligible. This work demonstrates that it is possible to determine bicarbonate flux across basolateral membrane vesicles at pH and temperature values close to usual experimental conditions. 相似文献
8.
An ELISA for the identification of mosquito bloodmeals (MBM) is described. The technique makes use of commercial antisera and allows to investigate at least three different animal sources on the same MBM. The efficiency of identification is 100% for up to 20 hrs-digested MBM. 相似文献
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Structural Genes for a Newly Recognized Acetolactate Synthase in Escherichia coli K-12 总被引:23,自引:15,他引:8
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Maurilio De Felice John Guardiola Bruno Esposito Maurizio Iaccarino 《Journal of bacteriology》1974,120(3):1068-1077
Evidence is reported that shows the presence in Escherichia coli K-12 of a newly found acetolactate synthase. This enzyme is the product of two genes, ilvH and ilvI, both located very close to leu. Amber mutations have been found in both genes and therefore their products are polypeptides. Mutations in the ilvH gene cause the appearance of an acetolactate synthase activity which is relatively resistant to valine inhibition and can be separated by adsorption on hydroxylapatite from another activity present in the extract and more sensitive to valine inhibition than the former. A mutant altered in the ilvI gene was isolated among the revertants sensitive to valine inhibition of an ilvH mutant. Such a mutant lacks the resistant acetolactate synthase. A temperature-sensitive revertant of the ilvI mutant contained a temperature-sensitive acetolactate synthase. Thus ilvI is the structural gene for a specific acetolactate synthase. The activity of the ilvH gene product has been measured by adding an extract containing it to a purified ilvI acetolactate synthase, which, upon incubation, became more sensitive to valine inhibition. Conversely, a valine-sensitive acetolactate synthase (the product of the ilvH and the ilvI genes) became more resistant to valine inhibition upon incubation with an extract of a strain containing a missense ilvH gene product. 相似文献