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Biomedical subjects

I Tsukahara

Publications and source records attributed to I Tsukahara.

At least 19 recordsLinked to original sources
PubMed1992

Localization of nonspecific lipid transfer protein (nsLTP = sterol carrier protein 2) and acyl-CoA oxidase in peroxisomes of pigment epithelial cells of rat retina.

We investigated the localization of nonspecific lipid transfer protein (nsLTP) in rat retina, especially in the pigment epithelial (RPE) cells, by the avidin-biotin-peroxidase complex method on cryosections for light microscopy and by the cryoimmunogold method for electron microscopy. Light microscopic observation revealed that the RPE, inner segment layer, nerve fiber layer, and Müller cells contain nsLTP. In the RPE cells gold particles were exclusively concentrated in the small peroxisomes (microperoxisomes; 0.1-0.3 micron in diameter), which were identified by double staining using anti-nsLTP and anti-catalase antibodies. In the peroxisomes gold particles were distributed homogeneously in the matrices and no preferential binding to the limiting membrane was observed. Acyl-CoA oxidase was also localized in the matrices of the peroxisomes. We suggest that the peroxisomes in RPE cells play important roles in the metabolism of lipids of the outer segment disk membranes, especially in the beta-oxidation of polyunsaturated long-chain and very long-chain fatty acids, such as docosahexaenoic acid which is composed of approximately one third of fatty acids in the disk membranes.

Acyl-CoA Oxidase↗
PubMed1986

A new model for total cerebral ischemia in dogs.

We have developed a new method producing total cerebral ischemia (TCI) in dogs; clamping ascending aorta with aorto-atrial bypass formation. Clamping ascending aorta provides TCI, the duration of which can be controlled up to the periods of 10 min. Beyond this interval, it is difficult to maintain TCI because of heart failure from high afterload. Blood outflow from left ventricle is completely obstructed except for coronary circulation which is small relative to the blood volume expelled from left ventricle, even if venous return to the heart is reduced. Aorto-atrial bypass formation during aortic clamping provides two distinctive advantages. First, adjusting aortic pressure in an appropriate level low enough not to overload myocardium but still high enough to maintain sufficient coronary blood flow is possible by regulating the blood flow through the bypass tubing, and secondly drug administration and blood volume control is possible through the tubing. These result in better preservation of myocardium, enabling longer TCI and longer survivals after TCI. We were successful in having up to 18 min of TCI with this method. Seventy-five percent of dogs of 12 min TCI and 40% of 15 min TCI survived 7 days, limit of experiment, after TCI, but no dogs of 18 min TCI survived for more than 3 days.

Animals↗
PubMed1986

Effects of mannitol on cerebral circulation after transient complete cerebral ischemia in dogs.

The effects of hypertonic mannitol on postischemic cerebral circulation were studied in 20 dogs. Mannitol, 2 g/kg iv, was infused into ten dogs during a 2-h period starting 1.5 h after 6 min of complete cerebral ischemia. One hour postischemia, regional cerebral blood flow (rCBF) was 36% in the control group (ten dogs) and 39% in the mannitol group. In the control group, rCBF increased gradually thereafter to 70% of the preischemic value 10 h postischemia, whereas the restoration of rCBF was suppressed in the mannitol group. During the postischemic period, intracranial pressure (ICP) increased significantly in the control group, but it did not change significantly in the mannitol group. The effects of mannitol on rCBF and ICP in the present study can be explained primarily by decreased body water due to urinary loss. The administration of mannitol does not necessarily improve postischemic cerebral circulation.

Animals↗
PubMed1986

Metabolism of glycoproteins in cultured retinal pigment epithelium.

The turnover and migration of synthesized glycoproteins in the cultured retinal pigment epithelium have been studied. Quantitative study indicated that half-time of 3H-fucosylglycoproteins was 11.6 days. Autoradiography was performed several times after incubation of 3H-fucose. Retinal pigment epithelium constantly synthesized glycoproteins and released them into the basal extracellular material. Possible functions of the glycoproteins are discussed.

Animals↗
PubMed1986

Experimental chloroquine retinopathy.

Chloroquine retinopathy was produced experimentally in the eye of the albino corydoras (one of the tropical fish) by daily administration of chloroquine (0.1 mg per os). The enucleated eyes were examined from the 14th day to 3 months after the beginning of drug administration under light and electron microscopy. The first change of retina was the appearance of membraneous cytoplasmic body (MCB) in the cytoplasm of ganglion, amacrine, bipolar and horizontal cells. MCB might be degenerated lysosome. They showed lamellar figures or crystalline lattice-like structures. Secondarily, these MCB appeared in the inner segments of photoreceptor cells. The outer segments of rod cells disappeared, and then those of cone cells. Although photoreceptor cells were diminished in number in advanced degeneration, the cells of inner nuclear layer and ganglion cells were maintained in number. The presence of MCB dose not mean death of cells. The retinal pigment epithelial cells contained MCB in its cytoplasm only in severe degenerative cases, and did not show other remarkable changes. MCB also appeared in the cytoplasm of pericytes of retinal vessels. Chloroquine is considered to damage directly photoreceptor cells most severely.

Animals↗
PubMed1986

The degradation of alpha-crystallin at its carboxyl-terminal portion by calpain in bovine lens.

Bovine lens calpain (Ca2+-dependent cysteine proteinase; EC 3.4.22.17) was shown to catalyze limited proteolysis of A and B chains of alpha-crystallin in vitro. The sites of cleavages were determined by isolating and analyzing the peptide fragments formed using several different methods, including high-performance liquid chromatography, cyanogen bromide cleavage, and carboxypeptidase digestion. The results indicated that calpain cleaved both A and B chains at their respective carboxyl-terminal regions. A chain was cleaved at A(Arg163-Glu164) bond and A(Ser162-Arg163) bond, the former being split with 2.4 times preference over the latter. B chain was cleaved at B(Thr170-Ala171) bond and B (Arg163-Glu164) bond, the former being preferred 6.5 times. Peptide cleavage at any other sites were not detected by the present method of analysis.

Amino Acids↗
PubMed1985

Responsiveness of cerebral vessels to changes of blood pressure and partial pressure of carbon dioxide after a transient period of cardiac arrest in dogs.

Post-ischemic cerebral hypoperfusion supposedly due to constriction of cerebral vessels is considered to be one of the most important factors limiting the recovery of the brain after cerebral ischemia. An experimental study on dogs was carried out to determine the changes in the responsiveness of cerebral vessel to the dilating effects of increase of arterial pressure (AP) and of CO2 inhalation after 3-6 min of cardiac arrest. Responsiveness was measured by the ratio of change in intracranial pressure (ICP) to change in AP (delta ICP/delta AP) and to change in PCO2 (delta ICP/delta PCO2), since in a bony cranium the changes in cerebral vessel diameter are reflected by instantaneous ICP change. delta ICP/delta AP following the administration of intravenous epinephrine was 33%, 43%, 36%, 37% and 16% of pre-ischemic value 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. delta ICP/delta PCO2 following 10% CO2 inhalation was 13%, 32%, 55%, 50%, 70% and 75% of pre-ischemic value 1/2 h, 1 h, 2 h, 3 h, 4 h and 5 h after cerebral ischemia, respectively. Normal delta ICP/central venous pressure (delta CVP) was observed during the post-ischemic period, although statistical analysis was not done. From this we concluded: After 3-6 min of cardiac arrest, cerebral arteries constricted for more than 5 h during post-ischemic period. These arteries did not respond well to the dilating effects of increased arterial pressure or CO2 inhalation, but after 3 h their responses to CO2 inhalation returned to their pre-ischemic levels. The intracranial pressure became more or less dependent on CVP during post-ischemic period.

Animals↗
PubMed1985

Exocytosis by retinal pigment epithelial cells.

We observed cultured retinal pigment epithelial cells as they responded to the introduction of latex particles. The cells showed phagocytosis of particles 1 h after administration of latex and were filled with particles after 24 h. After 7 days, exocytosis of latex from basal plasma membrane was documented. Observation was repeated using a two-layer culture. 7 days after putting the retinal pigment epithelial layer containing latex particles on another layer without particles, we observed the appearance of latex particles in the lower layer that originally contained no particles. This demonstrated that cultured retinal pigment epithelial cells exocytose latex particles from basal cell membrane.

Animals↗
PubMed1985

Age-related changes of calpain II and alpha-crystallin in the lens of hereditary cataract (Nakano) mouse.

The age-related changes of calpain II (high-Ca2+-requiring form of Ca2+-dependent cysteine proteinase; EC 3.4.22.17) and alpha-crystallin in the lens of hereditary cataract (Nakano; cac/cac) mouse were studied. Before the onset of the cataract formation, i.e., at the end of the 2nd week after birth, the calpain activity in Nakano mice was as high as that in the control ICR mice, but it decreased rapidly as the cataract progressed to completion during the 4th and the 12th week. Marked degradation of lens proteins ensued between the 2nd and the 4th weeks, and one of these proteins was identified, using monospecific antibodies, as B chain of alpha-crystallin. A chain of alpha-crystallin was not degraded in vivo, in contrast to its known susceptibility to calpain in vitro. The present data suggest that in Nakano mice, calpain may be involved in the onset or early stage of the cataract formation.

Aging↗
PubMed1985

Distribution of calpain I, calpain II, and calpastatin in bovine lens.

Two types of Ca2+-requiring cysteine proteinase (calpain, EC 3.4.22.17), which required for full activation 100 microM Ca2+ (calpain I) and 1 mM Ca2+ (calpain II) were found to exist in the cytosolic fraction of bovine lens. Since calpain may play an important role on the degradation of lens proteins during the aging process of the lens, we attempted to study the distribution of calpain I, calpain II, and calpastatin (an endogenous specific inhibitor of calpain) in bovine lens. It was found that both the capsule-epithelium and cortex fiber cells contained calpains I and II and calpastatin, although the content of calpain I was much lower than that of calpain II. Calpains I and II and calpastatin activities were not detected in the nuclear region at all.

Animals↗