Search PubMed⌕ Search

Biomedical subjects

J Takagi

Publications and source records attributed to J Takagi.

At least 109 records · Page 6Linked to original sources
PubMed1987

Venom from southern copperhead snake (Agkistrodon contortrix contortrix). I. Characterization of a protease that preferentially releases fibrinopeptide B.

Using gel permeation chromatography with high performance liquid chromatograph (HPLC), a highly purified preparation of a protease has been obtained from the venom of the southern copperhead snake (Agkistrodon contortrix contortrix). Both gel permeation chromatography with HPLC and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that it had an apparent Mr of 60,000-64,000. It consisted of a single polypeptide chain. The activity was inhibited by dithiothreitol. It neither induced platelet aggregation nor activated plasma factor XIII. It cleaved fibrinopeptide B at a rate much faster than fibrinopeptide A from fibrinogen. This specificity was steadily lowered when the incubation temperature was elevated from 0 degrees C to 45 degrees C. Fibrinopeptides were released only at neutral pH.

Animals↗
PubMed1986

Interaction between plasma factor XIII and collagen.

Purified plasma Factor XIII efficiently bound to the immobilized collagen affinity column. In contrast, when plasma was applied to the column, as much as 80% of Factor XIII was not trapped. It was shown that the difficulty of binding of Factor XIII in plasma to collagen is not due to the covering of collagen with some plasma proteins. We then assumed that Factor XIII formed a complex in plasma with a certain protein(s), which would prevent Factor XIII from binding to collagen. Using an immobilized Factor XIII affinity column, we have indeed obtained one protein from plasma with apparent Mr of 260,000.

Animals↗
PubMed1986

Platelet factor XIII. The collagen receptor?

We have studied the binding of collagen fibers with platelet proteins using affinity chromatography on collagen-Sepharose. Only a few proteins from a platelet lysate were trapped by this column. When denatured collagen (gelatin) was used as the affinity ligand, the major protein did not bind and was identified as platelet Factor XIII by polyacrylamide gel electrophoresis, immunoprecipitation, and enzymic activity. This is a zymogen form of transglutaminase, which corresponds to the "a" subunit of the coagulation factor in plasma. Immunoglobulins specific for platelet Factor XIII obtained from antiserum raised against plasma Factor XIII were able to initiate platelet aggregation by themselves, in strong contrast to nonspecific antibodies. This specific immunoglobulin-mediated platelet aggregation required the presence of Ca2+. It was inhibited by aspirin and prostacyclin, but not by specific inhibitors for other agonists. These data suggest the possibility that the zymogen form of Factor XIII is located on the surface of platelets and may play a key role as the receptor for collagen-induced platelet aggregation.

Animals↗
PubMed1986

Specific desensitization in the cytoskeletal assembly of platelet by receptor-dependent activations.

Cytoskeletal assembly induced by receptor-dependent or independent activation of bovine platelets was investigated. When platelets were preactivated with receptor-dependent stimulus, ADP or thrombin, cytoskeletal assembly was not induced repeatedly by the same agonist. However, in the case of receptor-independent stimulus, cryo-activation, the assembly was induced not only by receptor-dependent but also by independent stimulus. The desensitization, therefore, lies in the transmission of stimuli from receptors to cytoskeletal proteins.

Actins↗
PubMed1986

Modification of transglutaminase assay: use of ammonium sulfate to stop the reaction.

An important modification was made of the assay for transglutaminase regarding dansyl cadaverine incorporation into casein. It is known that the amine, after incorporation into protein by transglutaminase, shows a marked increase of fluorescence accompanied by a slight blue shift. However, measurement of protein-bound fluorescence requires a rather complicated procedure, such as the precipitation by trichloroacetic acid or continually monitoring the fluorescence. To widen the applicability of the method, we utilized an excess concentration of ammonium sulfate to stop the reaction. At concentrations higher than 5 mM, the incorporation of the amine was completely stopped and the fluorescence was retained for more than 2 h. The fluorescence can be measured directly after stopping the reaction, so it has become feasible to assay many samples at a time. Furthermore, the sensitivity and reproducibility of the data were improved, since the reaction time could be prolonged and strictly defined.

Ammonium Sulfate↗