Morio Nakayama

We demonstrated that cardiac myoglobin participates in the selenium metabolism in rat hearts.

Gallium-68 (⁶⁸Ga) is a positron emitter for clinical positron emission tomography (PET) applications that can be produced by a ⁶⁸Ge/⁶⁸Ga generator without cyclotron. However, commercially available ⁶⁸Ge/⁶⁸Ga generator systems require multiple steps for the preparation of ⁶⁸Ga radiopharmaceuticals and are sometimes plagued by metallic impurities in the ⁶⁸Ga eluent. We developed a ⁶⁸Ge/⁶⁸Ga generator system using polysaccharide-based adsorbents and direct application of the generator-eluted ⁶⁸Ga-citrate to PET imaging of tropical infectious diseases. N-Methylglucamine (MG) as a ⁶⁸Ge-adsorbing unit (Sepha-MGs) was introduced to a series of Sephadex G-10, G-15, G-25, G-50, and G-75. In the batch method, over 97% of the ⁶⁸Ge in the solution was adsorbed onto the Sepha-MG series within 15 min. In particular, ⁶⁸Ge was effectively adsorbed on the Sepha(15)-MG packed columns and 70–80% of the ⁶⁸Ga was eluted by 1 mL of 0.1 M trisodium citrate with low ⁶⁸Ge contamination (68Ga solution was identified as ⁶⁸Ga-citrate. In PET studies, affected regions in mice infected with Leishmania and severe fever with thrombocytopenia syndrome virus were clearly visualized using the ⁶⁸Ga-citrate. Sepha-MGs are useful adsorbents for ⁶⁸Ge/⁶⁸Ga generator systems with high ⁶⁸Ga elution efficiency and minimal ⁶⁸Ge breakthrough. These results indicated that eluted ⁶⁸Ga-citrate can be directly used for PET imaging of infectious sites in mice. This novel generator system may be useful for straightforward PET imaging of infection in clinical practice.

In this article, we describe the development of a nanosized-glutathione peroxidase (GPx) mimic based on liposomes of which the amphiphilic selenenylsulfide derivative (R–Se–S–R′) was incorporated into a lipid membrane. A lipid membrane-compatible selenenylsulfide derivative, 1-oxo-headecyl-seleno-l-cysteine-methyl-Se-yl-S-l-penicillamine methyl ester (OHSeP), was synthesized. X-ray photoelectron spectroscopy revealed that the sulfur and selenium atoms of the OHSeP molecule formed a selenenylsulfide linkage. The use of OHSeP easily allowed the introduction of the seleno-l-cysteine (SeCys) moiety into the liposomal membranes by mixing with the phosphatidylcholines (PCs), which gave rise to the GPx-like catalytic activity because of the selenium atom in the SeCys moiety. The penicillamine moiety of the OHSeP molecule incorporated into the OHSeP/PC liposomes was thought to orient toward the outer water phase. The OHSeP/PC liposomes generated the GPx-like catalytic activity, which was ascribed to the SeCys moiety that was introduced into the PC-based liposomes. Consequently, the lipid/water interface of the liposomal membranes could possibly provide an effective colloidal platform for the development of water-soluble nanosized GPx mimics.