Biomedical subjects

Tetsuo Nagano

Publications and source records attributed to Tetsuo Nagano.

57 records · Page 4Linked to original sources

PubMed2001

Orthogonality of calcium concentration and ability of 4,5-diaminofluorescein to detect NO.

We have developed diaminofluoresceins (DAFs) and diaminorhodamines as fluorescent indicators for NO based on the specific reaction of the aromatic vicinal diamines with NO. Among them, 4,5-diaminofluorescein (DAF-2) is widely used for real-time biological imaging of NO in cultured cells or tissues by many researchers. Contrary to a recent report of divalent cation sensitivity and photoactivation of DAF-2 (Broillet, M. C., Randin, O., and Chatton, J. Y. (2001) FEBS Lett. 491, 227-232), our study using NO gas itself reveals that the reaction of DAF-2 and NO is completely independent of Ca2+ and Mg2+ at physiological concentrations. Ca2+ enhances not the conversion of DAF-2 into its fluorescent product (DAF-2 triazole) but the release of NO from NO donors. Therefore it is concluded that DAF-2 can provide reliable information on NO production in biological systems regardless of the dynamic changes of Ca2+ concentration.

Calcium↗

PubMed2000

Effects of tetrahydrobiopterin on endothelial dysfunction in rats with ischemic acute renal failure.

The role of nitric oxide (NO) in ischemic renal injury is still controversial. NO release was measured in rat kidneys subjected to ischemia and reperfusion to determine whether (6R)-5,6,7,8-tetrahydro-L-biopterin (BH4), a cofactor of NO synthase (NOS), reduces ischemic injury. Twenty-four hours after bilateral renal arterial clamp for 45 min, acetylcholine-induced vasorelaxation and NO release were reduced and renal excretory function was impaired in Wistar rats. Administration of BH4 (20 mg/kg, by mouth) before clamping resulted in a marked improvement of those parameters (10(-8) M acetylcholine, delta renal perfusion pressure: sham-operated control -45 +/- 5, ischemia -30 +/- 2, ischemia + BH4 -43 +/- 4%; delta NO: control +30 +/- 6, ischemia + 10 +/- 2, ischemia + BH4 +23 +/- 4 fmol/min per g kidney; serum creatinine: control 23 +/- 2, ischemia 150 +/- 27, ischemia + BH4 48 +/- 6 microM; mean +/- SEM). Most of renal NOS activity was calcium-dependent, and its activity decreased in the ischemic kidney. However, it was restored by BH4 (control 5.0 +/- 0.9, ischemia 2.2 +/- 0.4, ischemia + BH4 4.3 +/- 1.2 pmol/min per mg protein). Immunoblot after low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the dimeric form of endothelial NOS decreased in the ischemic kidney and that it was restored by BH4. These results suggest that the decreased activity of endothelium-derived NO may worsen the ischemic tissue injury, in which depletion of BH4 may be involved.

Acute Kidney Injury↗

PubMedDate not supplied

Light-harvesting ionic dendrimer porphyrins as new photosensitizers for photodynamic therapy.

Photodynamic therapy (PDT) is a promising therapeutic modality for treatment of solid tumors. In this study, third-generation aryl ether dendrimer porphyrins (DPs) with either 32 quaternary ammonium groups (32(+)DPZn) or 32 carboxylic groups (32(-)DPZn) were evaluated as a novel, supramolecular class of photosensitizers for PDT. DPs showed a different cell-association profile depending on the positive or negative charge on the periphery, and both DPs eventually localized in membrane-limited organelles. In contrast, protoporphyrin IX (PIX), which is a hydrophobic and relatively low molecular weight photosensitizer used as a control in this study, diffused through the cytoplasm except the nucleus. Confocal fluorescent imaging using organelle-specific dyes indicated that PIX induced severe photodamage to disrupt membranes and intracellular organelles, including the plasma membrane, mitochondrion, and lysosome. On the other hand, cells treated with DPs kept the characteristic fluorescent pattern of such organelles even after photoirradiation. However, notably 32(+)DPZn achieved remarkably higher (1)O(2)-induced cytotoxicity against LLC cells than PIX. Furthermore, both dendrimer porphyrins had far lower dark toxicity as compared with PIX, demonstrating their highly selective photosensitizing effect in combination with a reduced systemic toxicity.

Cell Membrane↗