[Experimental evaluation of low-dose aspirin used in microvascular surgery].

OBJECTIVE: To evaluate the effect of low-dose aspirin on the deposition of platelet at the anastomotic site and the function of coagulation system in order to provide experimental data for clinical use. METHODS: (1) Twenty-eight SD rats were divided into experimental group (n = 21) and control group (n = 7), aspirin were administered through a catheter placed in the femoral vein in dose of 4 mg/kg in the experimental group and the same dose of normal saline in the control group. The experimental group was subdivided into 3 groups, with 7 rats in each group, according to survival time of 24, 48 and 72 hours after dose. Samples of 4 ml blood were taken by heart puncture from each rat to investigate the maximal platelet aggregation rate(MAR), prothrombin time(PT) and kaolin partial thromboplastin time(KPTT). (2) Sixteen New Zealand White rabbits were divided into experimental and control group, 8 rabbits in each group. Drugs were given in the same way. Forty-eight hours later, the bilateral femoral arteries of each rabbit were exposed and arteries between inguinal ligament and the origin of the superficial epigastric arteries were transected and end-to-end anastomosis was completed with interrupted suturing technique. Fifteen and 120 minutes after the recovery of blood flow, the left and the right vessels containing anastomotic sites were harvested respectively and treated with 125I-labeled anti-GP IIb/III a antibody (SZ-21) using radioimmunobinding method. The radioactivities of the anastomosed vessels were measured. RESULTS: The KPTT in the experimental group was longer than that of the control group at 24- and 48-hour group, the mean percentages of increase were 42.56% and 35.33% respectively, and there were very significant differences between the experimental and control group in 24-hour group (P < 0.001). The PT value in experimental group was longer than that of the control group, but there was no significant difference (P > 0.05), and the maximal aggregation rate of platelet in the experimental group was significantly lower than that of the control group after 72 hours (P < 0.001). The radioactivity of the anastomosed arteries in the experimental group were significantly higher than that of the control group (P < 0.001) at 15 minutes after the recovery of blood flow, the mean percentage of increase was 110%. CONCLUSION: Low-dose aspirin can significantly affect the function of the intrinsic coagulation system, prevent the aggregation of platelets, but no effect on the function of the extrinsic coagulation system. On the other hand, it can also increase the deposition of platelet on the anastomotic sites after end-to-end anastomosis, especially in the early stage when it is intravenously injected, but it is strong enough to cause thrombosis at the anastomotic sites. The effects of low dose aspirin on the coagulation system are inconsistent with its local effects on anastomotic sites.

Comparison of 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-peptide-ChL6, a novel immunoconjugate with catabolizable linker, to 2-iminothiolane-2-[p-(bromoacetamido)benzyl]-DOTA-ChL6 in breast cancer xenografts.

Radioimmunotherapy using 131I-ChL6 antibody has shown promise in patients with breast cancer. To enhance this potential, a novel ChL6 immunoconjugate that is catabolizable and tightly binds 90Y and (111)In was developed. The immunoconjugate, 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-peptide-ChL6, consists of the macrocyclic chelator DOTA linked to ChL6 by a peptide that is preferentially catabolized in the liver. The pharmacokinetic and dosimetric properties of the radioimmunoconjugates (RICs) (111)In- and 90Y-DOTA-peptide-ChL6 and (111)In- and 90Y-2-iminothiolane (2-IT)-2-[p-(bromoacetamido)benzyl]-DOTA-ChL6 were compared in athymic mice bearing HBT3477 human breast cancer xenografts. Each of the RICs was stable in vivo and concentrated well in the xenografts. Liver concentration, cumulative radioactivity (activity over time), and radiation dose of the DOTA-peptide-ChL6 RICs were one-third to one-half of those of the corresponding 2-IT-2-[p(bromoacetamido)benzyl]-DOTA-ChL6 RICs. Indium-111 RICs were imperfect tracers for corresponding 90Y RICs, although their pharmacokinetics and radiation dosimetries were similar. The results of this study were consistent with previously published in vitro data, which indicated that the peptide linker of DOTA-peptide-ChL6 was catabolized by cathepsin B. The cumulative activities and radiation doses to the liver of DOTA-peptide-ChL6 RICs were one-half of those of corresponding RICs with the 2-IT linker. Preliminary data from pilot studies in patients with breast cancer are in accord with these observations. These novel DOTA-peptide RICs seem to have excellent clinical potential for radioimmunotherapy associated with marrow transplantation, for which liver radiation is likely to be dose limiting for 90Y.

Prelabeling of chimeric monoclonal antibody L6 with 90yttrium- and 111indium-1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraacetic acid (DOTA) chelates for radioimmunodiagnosis and therapy.

90Y and 111In have been attached to chimeric monoclonal antibody L6 with a bifunctional chelating agent (DOTA-peptide isothiocyanate). The bifunctional chelating agent was prelabeled with either radiometal and then conjugated to the antibody. Studies in human patients showed excellent 111In single-photon emission computed tomography images of breast cancer lesions 24 h after injection.

Pharmacokinetics of chimeric L6 conjugated to indium-111- and yttrium-90-DOTA-peptide in tumor-bearing mice.

UNLABELLED: A bifunctional chelating agent, DOTA-Gly3-L-(p-isothiocyanato)-phenylalanine amide (DOTA-peptide-NCS), was studied in nude mice bearing human breast cancer xenographs (HBT 3477) to determine its potential for radioimmunoconjugate therapy. METHODS: Indium-111 and yttrium-90 were attached to an anti-adenocarcinoma chimeric L6 (ChL6) monoclonal antibody (MAb) after pre-chelation to the DOTA-peptide-NCS and the desired neutral radiochelates were obtained by purification. The unique characteristic of the DOTA-peptide-NCS to form neutral complexes with trivalent metals was utilized to separate the resulting 111In and 90Y radiochelates from excess chelating agent and other anionic by-products resulting from metal impurities. The purified radiochelates were then conjugated to ChL6. The pharmacokinetics of 111In- and 90Y-DOTA-peptide-ChL6 were obtained for 5 days after injection in nude mice bearing HBT 3477 xenographs. The results were compared with the pharmacokinetics of 125I-ChL6 obtained in the same mouse model. RESULTS: The whole-body clearance of 125I-ChL6, 90Y- and 111In-DOTA-peptide-ChL6 was monoexponential with biologic half-times of 92, 104 and 160 hr, respectively. Blood clearances of the three radiopharmaceuticals were biphasic. The radiometal immunoconjugates had greater tumor uptake and slower clearances. CONCLUSION: Indium-111- and 90Y-DOTA-peptide-ChL6 can be produced at high specific activity with fewer than one chelate per MAb by using a pre-labeling method that permits radiochelate purification by charge selection. Studies in mouse xenografts indicate that tumor uptake is enhanced and a favorable therapeutic index is achieved using these agents.

Labeling monoclonal antibodies with 90yttrium- and 111indium-DOTA chelates: a simple and efficient method.

Yttrium-90 and indium-111 have been attached to a monoclonal antibody with a bifunctional chelating agent (DOTA-peptide). Using the unique features of this DOTA-peptide and its complexes with trivalent yttrium and indium, the bifunctional chelating agent was prelabeled with either radiometal and then conjugated to chimeric monoclonal antibody L6. Both radiolabeling procedures and yield are suitable for the practical preparation of radiopharmaceuticals. Biodistribution studies in tumor-bearing mice showed that, e.g., on day 3 after intravenous injection of a 90Y immunoconjugate, liver uptake was 5.4 +/- 1.5% ID/g, bone uptake 2.0 +/- 0.5% ID/g, and tumor uptake 18.0 +/- 8.0% ID/g.