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Biomedical subjects

T Ahn

Publications and source records attributed to T Ahn.

27 records · Page 2Linked to original sources
PubMed1996

Conformational change of cytochrome P450 1A2 induced by sodium chloride.

Recently, it was reported that the activity of rabbit P450 1A2 is markedly increased at elevated sodium phosphate concentration. Here, the possible structural change of rabbit P450 1A2 accompanying the NaCl-induced increase in its enzyme activity is investigated by fluorescence spectroscopy, circular dichroism, and absorption spectroscopy. It was found that NaCl increased alpha-helix content and lowered beta-sheet content of P450 1A2 in the presence as well as in the absence of a phospholipid. Intrinsic fluorescence emissions also increased with increasing NaCl concentration. The low spin iron configuration of P450 1A2 shifted toward the high spin configuration in response to the increased salt concentration. The effect of increased potassium phosphate and NaCl on the P450 1A2 activity was also studied. It was found that the activity increase of rabbit P450 1A2 occurs concomitantly with the conformational change including raised alpha-helix content.

Animals↗
PubMed1996

Differential effect of precursor ribose binding protein of Escherichia coli and its signal peptide on the SecA penetration of lipid bilayer.

Digestion of vesicle-bound SecA by trypsin entrapped within the vesicles showed that refolding precursor ribose-binding protein (pRBP) of Escherichia coli retards the lipid bilayer penetration by SecA while the signal peptide enhances it. This discrepancy was found to be due to reduced SecA binding to the vesicles in the presence of the pRBP while the signal peptide induced a tight binding. Studies on the binding of 1-anilino-8-naphthalene sulfonate (ANS) to SecA indicated that SecA assumes more closed conformation upon interaction with pRBP and signal peptide induces more open structure of SecA. Kinetic studies of ANS binding to SecA upon dilution of unfolded pRBP with SecA solution showed an initial fast ANS binding, which was followed by a slow release of ANS. This suggests that first the signal peptide portion of the pRBP binds with the SecA making its structure more open and then the subsequent binding of the mature domain makes the SecA structure more compact. The pRBP enhanced the digestion of SecA added to the E. coli inverted vesicles, suggesting an inhibition of SecA penetration while the signal peptide had an opposite effect, agreeing with the results from the model systems above. When the pRBP and ATP were present together, however, the penetration of SecA increased dramatically underlining the importance of the SecY/E complex for the membrane insertion of SecA.

Adenosine Triphosphatases↗
PubMed1994

SecA of Escherichia coli traverses lipid bilayer of phospholipid vesicles.

SecA protein of Escherichia coli, when added externally to the vesicles composed of phosphatidylethanolamine, dioleoylphosphatidylglycerol and cardiolipin, was found to be fragmented by trypsin encapsulated within the vesicles. In the presence of ATP or its non-hydrolyzing analogue, ATP-gamma S, the number of fragments and extent of hydrolysis occurred much less than in the absence of these compounds. When ADP was added, however, the hydrolysis products were similar to those when no nucleotide was present. Quenching of SecA fluorescence by vesicle-entrapped iodide corroborated the digestion results. These experiments demonstrated that the SecA protein traverses the lipid bilayer and its membrane topology depends on the kind of nucleotide present.

Adenosine Triphosphatases↗
PubMed1991

Urinary pepsinogen I as a tumor marker of stomach cancer after total gastrectomy.

The possibility that urinary pepsinogen I is a tumor marker of stomach cancer after total gastrectomy was examined. To decide the cutoff level of urinary pepsinogen I after total gastrectomy, urine samples from 15 patients who had undergone total gastrectomy for stomach cancer in the early or advanced stages and had been free from recurrence for more than 5 years were examined by pepsinogen I-specific radioimmunoassay. The mean concentration of urinary pepsinogen I was 17.5 +/- 7.4 ng/ml and the cutoff level of urinary pepsinogen after total gastrectomy was set at 32 ng/ml (mean + 2 SD). Twenty-two of 74 cases who had undergone total gastrectomy for stomach cancer were regarded as positive. And 20 of these 22 positive cases had definite clinical signs of recurrence of stomach cancer. There were only two false-positive cases. These results suggest that urinary pepsinogen I will be an useful tumor marker in detecting the recurrence of stomach cancer after total gastrectomy.

Adenocarcinoma↗
PubMed1988

[Anti-cancer efficacy of peplomycin, adsorbed on activated carbon particles, against lymph node metastases in mice].

PEP-CH is comprised of activated carbon particles that adsorb peplomycin. Mice which were inoculated with 5 x 10(5) MH 134 tumor cells subcutaneously opposite the foot-pad of the left hind paw on day 0, received a subcutaneous injection of peplomycin, 0.25 mg/mouse, in the form of PEP-CH or a peplomycin aqueous solution administered at the foot-pad of the left hind paw on day 10. The left popliteal lymph nodes then were transferred intraperitoneally to normal mice on day 14. In the PEP-CH group, the survival time of the recipients was statistically and significantly long, and the transferred tumor cell number, estimated with a calibration curve, was markedly small when compare to mice in the other treatment groups.

Animals↗
PubMed1987

Localization of radiolabeled monoclonal antibody S74 in human scirrhous type gastric cancer xenografts in nude mice.

A mouse monoclonal antibody (MoAb), S74 against a human scirrhous gastric carcinoma cell line was developed. The radioiodinated antibody bound preferentially in vivo to xenografted tumors rather than to normal tissue, whereas tumor uptake of normal mouse IgG did not occur. Thus this MoAb was able to selectively localize a human tumor in an animal model, and clinically it may enable immunotherapy against scirrhous carcinoma of the stomach.

Adenocarcinoma, Scirrhous↗
PubMedDate not supplied

Anticancer agents adsorbed by activated carbon particles, a new form of dosage enhancing efficacy on lymphnodal metastases.

A new dosage form consisting of small activated carbon particles which adsorb Aclacinomycin A, Adriamycin, Mitomycin C or Pepleomycin was prepared in order to deliver larger amounts of anticancer agents to the lymph nodes through the high ability of lymphatics to adsorb particles. Animal experiments showed that: The LD50 values of the new dosage form were higher than those of the dosage in solution. The concentration of agents in lymph nodes was maintained at a higher level in the new dosage form than in solution form. Clinically 33% of lymphnodal metastatic lesions became degenerative or inflammatory after a single administration.

Aclarubicin↗