Ikuko Nakagaki

Calpain inhibitor entrapped in liposome rescues ischemic neuronal damage

Transient forebrain ischemia induces activation of calpain and proteolysis of a neuronal cytoskeleton, fodrin, in gerbil hippocampus. This phenomenon precedes delayed neuronal death in hippocampal CA1 neurons. We examined effects of a calpain inhibitor on delayed neuronal death after transient forebrain ischemia. In gerbils, a selective calpain inhibitor entrapped in liposome was given transvenously and 30 min later, 5-min forebrain ischemia was produced by occlusion of both common carotid arteries. On day 7, CA1 neuronal damage was examined in the hippocampal slices stained with cresyl violet. Calpain-induced proteolysis of fodrin was also examined by immunohistochemistry and immunoblot. Additionally, to assure entrapment of the inhibitor by CA1 neurons, the inhibitor-liposome complex was labeled with FITC and given to gerbils. Fluorescence in the hippocampal slices was examined by confocal laser scanning microscope. Selective CA1 neuronal damage induced by forebrain ischemia was prevented by administration of the inhibitor in a dose-dependent manner. Calpain-induced proteolysis of fodrin was also extinguished by the calpain inhibitor in a dose-dependent manner. Bright fluorescence of the FITC-labeled inhibitor was observed in the CA1 neurons. The data show an important role of calpain in the development of the ischemic delayed neuronal death. Calpain seems to produce neuronal damage by degrading neuronal cytoskeleton. Our data also show a palliative effect of the calpain inhibitor on the neurotoxic damage, which offers a new and potent treatment of transient forebrain cerebral ischemia.

Changes in element concentrations induced by agonist in pig pancreatic acinar cells

Changes in electrolytes of pig pancreatic acinar cells following application of gastrin-cholecystokinin (CCK) were investigated using the technique of X-ray microanalysis of hydrated and dehydrated sections of freshly frozen pancreas. After stimulation by CCK (10−9 M), Na and Cl increased significantly in the cytoplasm [Na, from 10 mmol/kg wet wt. (48 mmol/kg dry wt.) to 19 mmol/kg (95 mmol/kg); Cl, from 22 mmol/kg (105 mmol/kg) to 49 mmol/kg (245 mmol/kg)] as well as in the luminal interspace [Na, from 53 mmol/kg (189 mmol/kg) to 65 mmol/kg (283 mmol/kg); Cl, from 65 mmol/kg (232 mmol/kg) to 102 mmol/kg (443 mmol/kg)]. In the secretory granules Cl increased significantly from 30 mmol/kg (86 mmol/kg) to 67 mmol/kg (203 mmol/kg). K decreased significantly from 120 mmol/kg (571 mmol/kg) to 81 mmol/kg (405 mmol/kg) in the cytoplasm, while both increased from 38 mmol/kg (109 mmol/kg) to 58 mmol/kg (176 mmol/kg) in the granules and from 46 mmol/kg (164 mmol/kg) to 48 mmol/kg (209 mmol/kg) in the luminal interspace. Ca increased significantly in the cytoplasm as well as in the luminal interspace, and decreased significantly in the secretory granules. CCK evoked Ca release from secretory granules in the secretory pole of acinar cells. The values were measured from dehydrated sections, and agreed well with those from hydrated sections. The effect of furosemide, an inhibitor of the Na+-K+-2Cl− co-transporter, on the ion transport of acinar cell was studied. When furosemide (10−5 M) was added to the external solution, the cytoplasmic Cl and Ca concentrations decreased significantly, while there was a little decrease in Na and K concentrations under the secretory condition. These results indicate that Na+-K+-2Cl− co-transport, and Na+, Cl− and K+ exits into the lumen are involved in the mechanism of ion secretion in pig pancreatic acinar cells.

Histochemical and cytochemical localization of (Na+-K+)-activated adenosine triphosphatase in the acini of dog submandibular glands.

p-Nitrophenyl phosphatase (p-NPPase) activity of (Na+-K+)-activated adenosine triphosphatase ((Na+-K+)-ATPase) on the acinar cells of dog submandibular gland was demonstrated by using light microscopy. The reaction products of p-NPPase of fresh frozen sections were seen to be localized on the basal parts of acini, and disappeared when the sections were incubated in medium containing 10(-3) Mouabain or in a K-free medium. Under the electron microscope, the reaction products of ATPase were found to be localized on the basolateral plasma membrane of both serous and mucous cells. On the microvilli of the luminal plasma membrane of the acinar cell, a small quantity of the reaction products was also present. This localization of ATPase reaction products on the serous and mucous cells seemed to coincide well with that of p-NPPase activity observed on the acini under light microscopy. Possible explanations are given regarding distribution of the above mentioned enzymes in relation to the cation transport of the plasma membrane. Structural and functional asymmetrical properties of acinar cells of the dog submandibular gland are also discussed.

Effects of the endothelin receptor antagonist TAK-044 on hepatocyte element alterations in the ischemic-reperfused liver in Beagle dogs

BACKGROUND/AIMS This study was designed to investigate elemental alterations of subcellular organelles (cytoplasm, nucleus, mitochondria) after ischemia of the liver, and the effects of the pre-ischemic administration of an endothelin ETA/ETB receptor antagonist (TAK-044) on subcellular elements. METHODS We determined serial changes in subcellular elements by X-ray microanalysis using liver biopsy specimens, and we compared the liver functions of a control and a TAK-044-treated group of Beagle dogs, before and after 70% partial ischemia (60 min). TAK-044 was given intravenously at a dose of 3 mg/kg before ischemia. RESULTS In the control, the Ca concentration in the cytoplasm showed a slight increase after ischemia and a marked increase immediately after reperfusion. It returned to approximately pre-ischemic levels at 6 h after reperfusion. In contrast, in the TAK-044 group, the increase was significantly suppressed. The changes in Na and Cl, which increased in parallel with Ca, were also suppressed in the TAK-044 group. The alterations in K were opposite to those Ca. These changes were also suppressed to a significant degree in the TAK-044 group. Elemental alterations in the nucleus and mitochondria were similar to those in the cytoplasm in both the control and TAK-044 groups. The changes in the liver functions and the electron microscopic findings supported the differences in serial changes in subcellular elements between the two groups. CONCLUSIONS TAK-044 exhibited a hepatoprotective effect on ischemia-reperfusion injury from the aspect of subcellular elemental dynamics and liver functional and morphologic changes.

Extracellular and intracellular ion concentration of Octopus visual cells and ion permeability of the cell membranes

Abstract Sodium, potassium, chloride, calcium, magnesium and sulphate concentrations in the vitreous humour and retina of Octopus vulgaris were measured by flame photometry. The density and dry mass fraction of the dark-adapted retina were determined to be 1.074 ± 0.027 g cm−3 and 22.4% ± 0.6% respectively. Those of the vitreous humour were 1.033 ± 0.002 g cm−3 and 3.0% ± 0.2% respectively. Subsequent calculations yielded an interstitial space of the retina of 19% (v/v). Using this value of the interstitial space, the intracellular ion concentrations of the dark-adapted and illuminated retinas were determined. These ion concentrations were used, together with the membrane potentials obtained from electrophysiological experiments, to calculate the ion permeability of Octopus visual cell membranes in the dark and on flash illumination.

In vivo subcellular elemental dynamics in liver graft: With special reference to effect of non-selective endothelin receptor antagonist, TAK-044, on the graft injury

Background: No data are available concerning the in vivo subcellular dynamics of elements in liver grafts and the effect of endothelin receptor antagonist, TAK-044, against graft injury. Methods: Liver transplantation was performed in porcine under active veno-venous bypass. The grafts stored in chilled preservation solution were recirculated following reflush with lactated Ringers solution with or without TAK-044 (10 mg/kg). Cold and warm ischemic times of the grafts were comparable between the two groups. Elements (Na, K, Cl, Ca, P and S) were measured in three fractions of cytoplasm, mitochondria and nucleus by electron probe X-ray microanalysis for the graft biopsy specimens obtained at various time from donor laparotomy to 1 week after liver grafting. Liver functions also were compared between the two groups. Results: In both groups, concentration of each element changed in parallel among the three subcellular fractions and their changes were less marked in the nucleus. In the control group, there were significant increases in cytoplasmic Na and Cl after portal reperfusion and in cytoplasmic and mitochondrial Ca after hepatic artery reperfusion. These were accompanied by K and mitochondrial S decreases without a statistical significance. In the TAK group, such postreperfusion elemental alterations were significantly suppressed and early deterioration of the liver functions was alleviated, as compared with the control group. Conclusion: A supplemental use of TAK-044 in a rinse solution before reflush contributed to stability of subcellular elements after reperfusion and better preservation of early graft function.