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Biomedical subjects

K Tagawa

Publications and source records attributed to K Tagawa.

At least 181 records · Page 10Linked to original sources
PubMed1981

Binding of intrinsic ATPase inhibitor to mitochondrial ATPase--stoichiometry of binding of nucleotides, inhibitor, and enzyme.

F1-ATPase inhibitor was purified from yeast, Saccharomyces cerevisiae. The purified inhibitor blocked ATPase activity in the presence of ATP and Mg2+ by forming a latent equimolar enzyme-inhibitor complex with ATP and ADP newly bound to loose sites on the enzyme. A small portion of externally added ATP was hydrolyzed before the latent complex was formed but the hydrolysis was not directly related to the complex formation. Newly bound ATP tended to be converted to ADP when the ATP concentration of the medium was low. ATP tightly bound to the enzyme was not directly involved in formation of the complex. The complex was fairly stable in the presence of excess inhibitor and ATP but at a high concentration of the enzyme (10(-5) M), the inhibition was not complete, although only about 0.03% of the original activity remained unblocked.

Adenosine Diphosphate↗
PubMed1981

Amino acid sequence of an intrinsic inhibitor of mitochondrial ATPase from yeast.

The amino acid sequence of an intrinsic inhibitor of mitochondrial ATPase isolated from yeast was completed by using solid-phase sequencing and conventional procedures. The inhibitor was found to be composed of 63 amino acid residues, to lack tryptophan, cysteine, and tyrosine, and to have a molecular weight of about 7,383. The inhibitor was characterized as a basic protein with 16 basic and 13 acidic amino acid residues, and several clusters of basic residues were noted. Some comments are made on the hydrophobic amino acids and the presence of repeated sequences.

Adenosine Triphosphatases↗
PubMed1980

A direct colorimetric method for the determination of phospholipids with dithiocyanatoiron reagent.

A simple and sensitive colorimetric method for the quantitative determination of phospholipids in various kinds of biological materials is described. The method, modification of a previous method using tetrathiocyanatocobaltate, is based on the formation of hydrophobic complexes between dithiocyanatoiron reagent and phospholipids. Under the standard conditions all species of neutral phospholipids, including lysophosphatidylcholine and sphingomyelin, form stable hydrophobic complexes with the iron compound. Although species of acidic phospholipids also have slight affinity for the iron compound, they do not disturb the assay appreciably, because their contents in biological materials are low. Under special conditions, the iron compound reacts only with phosphatidylcholine, and therefore it may also be used for specific determination of this phospholipid.

Colorimetry↗
PubMed1979

A simple method for measuring phosphatidylcholine as its hydrophobic complex with tetrathiocyanatocobaltate.

A sensitive colorimetric method for quantitative determination of phosphatidylcholine is described. The procedure is very simple, not involving lipid extraction or acid digestion, and can be used for direct estimation of phosphatidylcholine in blood plasma. The method depends on the formation of a stable hydrophobic complex of phosphatidylcholine with tetrathiocyanatocobaltate. Similar complexes are formed by other species of diacylglycerophosphoryl esters, but the absorbance coefficients of these complexes are only 10 to 20% of that of the phosphatidylcholine complex. Phospholipids without unsaturated fatty acids, such as dipalmitoyl phosphatidylcholine, do not form hydrophobic complexes. Lysophosphatidylcholine and sphingolipids also do not form similar complexes.

Animals↗
PubMed1979

Posterior cerebral artery occlusion: clinical, computed tomographic, and angiographic correlation.

The distribution of low-density areas on computed tomography (CT) suggested occlusions in the proximal half of the circummesencephalic portion in 38 patients with posterior cerebral artery (PCA) occlusion. Correlation between clinical, CT, and angiographic findings in 24 cases showed that occlusion was most common in the crural segment. Clinical manifestations and infarction extension varied widely among proximal occlusions. In cases with good collateral filling, the infarction was restricted to the thalamus; in those with poor filling, it involved most of the PCA's territory, and hemorrhagic transformation occasionally ensued. Discrepancies between findings were ascribed to dislodging of emboli or thrombi, recanalization, and transient obscuration of the infarction on CT.

Aged↗
PubMed1979

Interaction of mitochondrial aspartate aminotransferase with negatively charged lecithin liposomes.

Several kinds of hydrophilic proteins were examined to determine their interaction with artificial liposomes. Mitochondrial aspartate aminotransferase (m-GOT) [EC 2.6.1.1], as well as cytochrome c, was found to interact strongly with negatively charged liposomes. In each case, an appreciable amount of the protein bound to liposomes remained unreleased after raising the salt concentration in the medium. The m-GOT tightly bound to the liposomes was also found to become latent in its enzymatic activity, and could be reversibly activated by solubilization of the liposomes with detergent. This is also the case for cytochrome c, which ceases to be reducible by external reductant, such as dithionite. Furthermore, the tightly bound m-GOT was not susceptible to the proteolytic action of trypsin, or that of Nagarse. From these observations it can be inferred that these basic proteins interact with acidic liposomes not only electrostatically but also hydrophobically. This kind of hydrophobic interaction was not observed in the combination of positively charged liposomes and acidic proteins, including s-GOT. Mitochondrial GOT was shown to be bound to isolated intact mitochondrial, but the bound enzyme was fully active, in contrast to the case of acidic liposomes. The hydrophobic interaction of water-soluble protein with liposomes is discussed in connection with the penetration of matrix enzyme through mitochondrial membranes.

Aspartate Aminotransferases↗
PubMed1979

[Changes in plasma dopamine-beta-hydroxylase activity in patients with acute subarachnoid hemorrhage (author's transl)].

In 24 patients with subarachnoid hemorrhage (SAH) who were admitted within 48 hours after the onset, the activity of dopamine-beta-hydroxylase (DBH) in peripheral venous plasma was analyzed applying the method described by Nagatsu and Udenfriend (Clin. Chem., 18: 980-983, 1972) with a minor modification. Plasma samples were serially collected every a few days for three days to four weeks after the onset. DBH activity in peripheral venous plasma increased markedly after the onset, reaching the highest level within 48 hours, and thereafter declined time-dependently for about two weeks. There was no significant difference in the plasma DBH activities on admission between patients with and without cerebrovascular spasm revealed by angiography. The decline of the activity was significantly remarkable in patients with spasm compared with those without spasm. The difference was most prominent around the 7th day after the onset when spasm was shown most frequently. Neurosurgery or administration of analgesics and/or sedatives had little effect on the changes in plasma DBH activity in acute SAH. The activity correlated with the pressure of cerebrospinal fluid (r = 0.587, P less than 0.05), when it was higher than the normal range. With these results we obtained following: 1) The activity of sympathetic nervous system increases following SAH for a week after the onset. 2) The activity declines more rapidly in patients with cerebrovascular spasm than those without spasm, when it was judged from the activity of plasma DBH activity.

Acute Disease↗
PubMed1975

Development of mitochondrial membranes in anaerobically grown yeast cells.

Biochemical analyses of mitochondrial marker substances, especially cardiolipin and oligomycin-sensitive ATPase [EC 3.6.1.3], as well as electron microscopic observations were carried out to eludicate the process of mitochondrial development in annaerobic yeast cells. Cardiolipin was found to be localized in the mitochondria in anaerobic cells. Its cellular content was a little higher in the stationary phase than in the exponential phase in glucose-grown cells and increased further in galactose-grown cells. The lipid content of the mitochondrial preparation obtained from glucose-grown stationary cells was nearly as high as that from galactose-grown cells. It was also comparable to that of aerobic cells in the stationary phase, where mitochondria are fully developed. Both cellular and mitochondrial levels of oligomycin-sensitive ATPase activity were also found to rise markedly in galactose-grown anaerobic cells, although not in stationary phase cells grown anaerobically on glucose. These high levels of the mitochondrial markers indicate a developmental change in mitochondrial structure even in anaerobically grown cells, which lack mitochondrial cytochromes. In the process of aerobic adaptation, respiratory system formation was observed to occur much faster in galactose-grown cells than in glucose-grown cells, and not to be inhibited by chloramphenicol and high concentrations of glucose structure in anaerobic cells. The developmental change was also corroborated by electron microscopic observations, which revealed the occurrence of two types of mitochondria in anaerobic cells. One was found in glucose-repressed cells and was characterized by the presence of numerous electron-dense granules in the matrix. In contrast, the other type, found in glucose-derepressed cells, had an electron-lucent matrix. No crista membrane was seen in either type of mitochondria in anaerobic cells, although the infoldings of the inner membrane, which partition the matrix into two parts and therefore are called "septum membranes," appeared frequently in the stationary phase cells. On the basis of these results, the process of mitochondrial development in yeast cells is discussed.

Adenosine Triphosphatases↗