A new drug delivery system for local cancer chemotherapy using cisplatin and chitin.

A new drug delivery system for local cancer chemotherapy was developed by chemical combination of chitin and cisplatin. When this material (Plachitin) was implanted in mice, high cisplatin concentrations were measured in the tissue around Plachitin for more than eight weeks without any nephrotoxicity. Local application of Plachitin improved the survival of mice previously implanted with Ehrlich tumor (p < 0.05). The present study indicates that Plachitin is a useful local agent for solid tumors due to its slow and sustained release of a large amount of cisplatin around the tumor without systemic side effects.

[A new trial of plachitin particles for intraarterial chemoembolization therapy in rabbit].

Plachitin, which is reconstituted by the combination of CDDP and chitin, has been reported to have a slow releasing property of CDDP and an antitumor effect. The antitumor effect and pharmacokinetics of Plachitin for intraarterial chemoembolization therapy were studied in rabbits using VX2 tumor inoculated in the hind limb. One gram of Plachitin contained 300 mg CDDP, and the form of Plachitin was modified into particles (about 50 microns in diameter). Plachitin was injected into the femoral artery. The study was carried out in four groups. The tumor growth ratio was significantly lower in the Plachitin group than in the CDDP, chitin, and control groups (p < 0.05). Tumor regression was noticed only in the Plachitin group. The tumor platinum (Pt.) level was higher than the serum Pt. level for 5 days after Plachitin injection. From the above results it can be concluded that Plachitin particles released CDDP slowly around the tumor and the tumor growth was suppressed by the additive effect of CDDP and embolization. Plachitin was considered a useful agent for chemoembolization therapy for the cancer patients.

[Slow releasing anticancer drug containing CDDP for intraoperative use in residual cancer cells].

We have already reported the slow releasing property and anticancer effect of Plachitin, which is reconstituted by combination of CDDP and chitin. This study deals in more detail with the slow releasing property, and the renal complications and the effectiveness for solid tumor were examined. After implantation of Plachitin subcutaneously in the abdominal wall, the platinum concentration in the different organs was measured. In the abdominal muscle around the implanted Plachitin, a high concentration of platinum was maintained until 8 weeks and the peak was 4 weeks after implantation. At the same time, the serum concentration of platinum remained low. In kidney, the platinum concentration resembled the levels in the abdominal muscle, but no renal dysfunction was found serologically or histologically. When Plachitin was implanted around the solid tumor, the survival rates were improved and the gain in tumor weight was suppressed as compared with the controls. From these findings, Plachitin seemed to be effective as a slow releasing anticancer drug for topical application.

[An effective concentration method for human immunodeficiency virus type 1 (HIV-1)].

We designed an effective virus concentration method to prevent the infection with human immunodeficiency virus type 1 (HIV-1) in laboratories. The absorbent of Minicon concentrators (Amicon Division, M.R. Grace & Co.-Conn.) was changed to chitin, a mucopolysaccharide extracted from the shells of Japanese pink crab. HIV-1 in the supernatant of HIV-1 infected Molt-4 cells was concentrated by Minicon and the new concentrators. The new concentrator showed good concentration rate and equality of concentration speed.

[Development of slow releasing anticancer drug based with absorbable biomaterial chitin].

To have a comparatively more slowly releasing anticancer drug with effectiveness, Plachitin was prepared by chemical combination of CDDP and chitin (poly-N-acetyl-D-glucosamine). Chitin is absorbed by the living body over several months. To investigate the slow releasing property, it was implanted in thigh muscle of mice and rabbit. Pt level in different organs and in urine was measured at regular intervals. Pt level in implanted muscles was higher in comparison to low serum level in mice. It was released slowly over 1 to 2 months in mice, whereas in rabbit it took about three weeks. Pt releasing period of the Plachitin was different according to the adopted method of implantation. Anticancer effect of Plachitin was investigated by injecting 180 sarcoma cells in mouse peritoneal cavity and subsequent implantation of Plachitin. In control groups chitin was used instead of Plachitin. The survival rate of mice in the Plachitin group after 14 days was higher than in the chitin group, and the anticancer effect of the Plachitin was confirmed.

Bacillus stearothermophilus glyceraldehyde-3-phosphate dehydrogenase as a source of angiotensin-converting enzyme inhibitors.

The more potent inhibitory activity against angiotensin-converting enzyme (ACE) was excised from a glyceraldehyde-3-phosphate dehydrogenase (GAPDH) preparation of Bacillus stearothermophilus by heating at 120 degrees C in 1 M AcOH-20 mM HCl, as compared with GAPDH preparations of yeast and pig. Sufficient excision of B. stearothermophilus ACE inhibitors required a longer proteolysis time of 60 min. Two inhibitors were then purified by gel-permeation and reverse-phase chromatographies. One of the B. stearothermophilus ACE inhibitors BG-1, was the GAPDH peptide 68-77 (Gly-Lys-Glu-Ile-Ile-Val-Lys-Ala-Glu-Arg, IC50: 32 microM). Another inhibitor, BG-2 (Gly-Lys-Met-Val-Lys-Val-Val-Ser-Trp-Tyr, IC50: 6 microM), correspond to GAPDH peptide 304-313. These sequences were quite different from those of vertebrate GAPDH peptides and the venom peptide family with ACE inhibitory activity. BG-2 was found to be a non-competitive type inhibitor, differing from many natural peptide inhibitors. Thus, B. stearothermophilus GAPDH seemed to be a good source of new type ACE inhibitors, in addition to the advantages due to its thermophilic property.

A novel method for the synthesis of kyotorphin, Tyr-Arg, and 3H-Tyr-Arg, catalyzed by tyrosyl-tRNA synthetase from Bacillus stearothermophilus.

A novel method of dipeptide synthesis is described that can be carried out in aqueous solution and does not require complicated protecting and deprotecting procedures. An analgesic neuropeptide named kyotorphin, H-Tyr-Arg-OH, was synthesized from unprotected tyrosine and arginine in a new enzymatic reaction catalyzed by immobilized tyrosyl-tRNA synthetase from Bacillus stearothermophilus. The reaction could be a useful tool in the syntheses of radioisotope-labeled oligopeptides to be used in receptor binding assays. 3H-Kyotorphin was prepared by this method at a yield of 72% and could be used in receptor binding assays after a single chromatographic separation.

Dipeptide synthesis catalyzed by aminoacyl-tRNA synthetases from Bacillus stearothermophilus.

A new approach to enzymatic peptide synthesis by using aminoacyl-tRNA synthetase (ARS) as a catalyst has been investigated. Four ARSs (AspRS, HisRS, LeuRS and TyrRS) have been purified from a thermophilic bacterium, Bacillus stearothermophilus. By using TyrRS as a catalyst, tyrosine and leucinamide were shown to be condensed in the presence of ATP to give tyrosylleucinamide. In this manner, all of the ARSs investigated catalyzed the peptide synthesis reactions. TyrRS did not have strict specificity for the amino acid derivatives used as substrates and even D-amino acids were incorporated into peptides fairly easily in this enzymatic reaction. Preparative scale synthesis of L-Tyr-L-LeuNH2 was carried out and from this the scope and limitation of this new enzymatic reaction as a tool to the peptide synthesis has been described.

Reactions of the aminoacyl-tRNA synthetase-aminoacyl adenylate complex and amino acid derivatives. A new approach to peptide synthesis.

Several kinds of dipeptide derivative were shown to be formed by the reactions of the aminoacyl adenylate-aminoacyl-tRNA synthetase complex and amino acid ester or amide. It was shown that the peptide bond could be formed by aminoacyl-tRNA synthetases even in the absence of the ribosome.