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Biomedical subjects

K Koike

Publications and source records attributed to K Koike.

At least 883 records · Page 49Linked to original sources
PubMed1975

Static and functional morphology of the pathological platelets in primary myelofibrosis and myeloproliferative syndrome.

Native and functioning platelets in patients with primary myelofibrosis and myeloproliferative syndrome were examined by transmission electron microscopy. Among various types of ultrastructural abnormalities in the platelets, three features were emphasized: hypoplasia of the surface connecting system (SCS) with few orifices, hyperplasia of the dense tubular system, and considerable variety in numbers of granule. Morphological analysis was made on platelets of these patients and of normal subjects. Functional morphology of the abnormal platelets was examined in the aggregate samples either by ADP or collagen and the effluent blood from platelet retention test. The abnormal platelets were more or less indifferent from the aggregates and underwent only to a slight degree the changes observed in normal platelets. They frequently retained their native, round, smooth-surfaced form without pseudpod, and did not show the inward shift of organelles; furthermore, they retained more granules than did normal platelets. From these morphological findings we speculated that these ultrastructurally abnormal platelets had an impaired release reaction as a result of the dysfunction of SCS in passing released substances, of the inability of microfilaments to constrict in expelling these substances and sometimes because of a lack of granules as the sources.

Adenosine Diphosphate↗
PubMed1975

Purification properties and subunit composition of pig heart lipoate acetyltransferase.

Lipoate acetyltransferase [acetyl-CoA: dihydrolipoate S-acetyl-transferase, EC 2.3.1.12], the core enzyme of the pyruvate dehydrogenase complex, has been highly purified by gel chromatography on Sepharose 6B and sucrose density gradient centrifugation in the presence of potassium iodide. The native enzyme has a sedimentation coefficient (S020,W) of 26.7S and a diffusion coefficient (D020,W) of 1.25 x 10(-7) cm2.-sec-1. The weight-average molecular weight was estimated to be 1.8 million from the sedimentation equilibrium data. The content of right-handed alpha helix in the enzyme molecule was estimated to be about 25% by optical rotatory dispersion and about 22% from the circular dichroism spectra. The enzyme was found to contain about 23 moles of protein-bound lipoic acid per mole of enzyme; some other properties are also reported. Lipoate acetyltransferase dissociated to yield a single subunit with a molecular weight of 74,000 as estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and by gel filtration on Bio-Gel in 6 M guanidine-HCl. The molecular weight was also estimated to be 74,000 from sedimentation equilibrium data in 6 M guanidine-HCl] containing 0.1 M 2-mercaptoethanol. Evidence is presented that 1 molecule of lipoate acetyltransferase apparently consists of 24 very similar subunits, each of which contains NH2-terminal alanine. Each subunit contains 1 molecule of covalently bound lipoic acid.

Acetyltransferases↗
PubMed1974

Evidence for discontinuous replication of circular mitochondrial DNA molecules from Novikoff rat ascites hepatoma cells.

Double-forked circular molecules of mitochondrial DNA (mtDNA) from rat tissues, indicated by their form and size to be replicative intermediates, are of two structurally distinct classes. Molecules of the first class are totally double stranded. Molecules of the second class are defined by one daughter segment being totally or partially single stranded. Length histograms of daughter segments measuring between 2% and 44% of the total 5-microm molecular contour were constructed from samples of both classes of replicating molecules derived from mtDNA or Novikoff rat ascites hepatoma cells. For single strand-containing molecules, the lengths fell into eight distinct, reproducible groups with mean values separated by 4.1-7.6% of the circular contour length. For totally double stranded molecules, the lengths fell into seven groups, corresponding to seven of the groups found for single strand-containing molecules. These results suggest that along at least 44% of the contour of mtDNA molecules there exist discrete points at which DNA synthesis tends to be arrested. This may indicate that there are pauses in normal mtDNA synthesis. However, as the DNA used in these experiments was isolated from mitochondrial fractions, the findings may indicate that continuation of synthesis beyond specific points on the nucleotide strands requires a factor which is not available after cell disruption.

Animals↗