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Biomedical subjects

K Mitsui

Publications and source records attributed to K Mitsui.

At least 235 records · Page 13Linked to original sources
PubMed1979

Alteration of human erythrocyte plasma membranes by perfringolysin O as revealed by freeze-fracture electron microscopy. Studies on Clostridium perfringens exotoxins V.

When human erythrocyte membranes were treated with perfringolysin O (Clostridium perfringens theta-toxin) and examined by electron microscopy after freeze-fracture, two ultrastructural alterations were observed in fracture faces of membrane. (1) A random aggregation of intramembranous particles was seen in the fracture face of the protoplasmic half (PF face) of all membranes treated with the toxin, even if at a low concentration (40 hemolytic units/ml). On the other hand, the aggregation in the fracture face of the exoplasmic half (EF face) was observed only in membranes treated with a high concentration (3300 hemolytic units/ml) for 2 h. (2) Round protrusions and "cavities" with 30 nm in diameter were visible in EF and PF faces of membranes treated with a high concentration, respectively. These structures were always protruded toward cytoplasmic side, but did not appear to form holes through the membrane. Ring and arc shaped structures with a dark center of 26 nm and a distinct border of 5 nm in width were observed when the toxin alone was negatively stained at a very high concentration (170,000 hemolytic units/ml). These structures were also produced in the presence of cholesterol even if the toxin concentration was low.

Bacterial Toxins↗
PubMed1979

Clostridium perfringens exotoxins. VI. Reactivity of perfringolysin O with thiol and disulfide compounds.

The reactivity of perfringolysin O with thiol and disulfide compounds was studied. The activation potency of thiols was roughly proportional to the reaction rate constants of 5,5'-dithiobis-(2-nitrobenzoic acid) with thiols, which should be inversely proportional to their oxidation-reduction potentials. 1,2-Dimercaptoethane, which had the highest rate constant, most potently activated the toxin among the thiols tested and 4,4'-dipyridyl disulfide, which is known to be one of the most potent thiol-disulfide exchanging reagents, strongly inhibited toxin activity. Toxin activity was also inhibited by other thiol inhibitors.

Clostridium perfringens↗
PubMed1976

A prospective study of epilepsy following neonatal convulsions.

In a prospective study of 130 infants with neonatal convulsions, the frequency and type of epilepsy and the relationship between the presumptive etiology of neonatal convulsions and subsequent epilepsy were investigated in 82 survivors exclouding those dying and lost to follow-up. Of these 82 children, 15 (18.2%) were found to have epilepsy, which was of generalized type in seven (8.5%), infantile spasm in four (4.9%), focal seizures in three (3.6%) and myoclonic seizures in one (1.2%). Febrile convulf neonatal convulsions were asphyxia, intracranial hemorrhage or neonatal meningitides in most instances, but no particular relationship was noted between the presumptive etiology of neonatal convulsions and the type of subsequent epilepsy. In 11 (73.3%) of the 15 epileptic children, convurrent mental retardation, cerebral palsy and postmeningitic hydrocephalus were noted. Evidence from RI cisternography, pneumoencephalography and cerebral angiography indicated that perinatal or neonatal brain damage responsible for epilepsy might be organic in nature. The fact that epilepsy occurred later in many of cases of neonatal convulsions of unidentified etiology suggests that brain damage incurred during fetal life might also be implicated at least in some instances. The onset of epilepsy in this series was relatively early, invariably before three years of age.

Age Factors↗
PubMed1976

Clostridium perfringens exotoxins. IV. Inhibition of the theta-toxin induced hemolysis by steroids and related compounds.

1. The inhibitory powers of thirty two samples of steroids and their related compounds on the theta-toxin induced hemolysis were assayed. Apparent I50 value of cholesterol, the most potent inhibitor amoung them, was 0.022 muM. 2. Inhibitory powers of sterol acetates were not more than one tenth of those of the corresponding sterol, and steroids without 3-hydroxyl group hardly inhibited the hemolysis. These results suggest that 3-hydroxyl group of sterols plays an important role in the inhibition. 3. The inhibitory power of sterols were strongly affected by steric situation of 3-hydroxyl group for the face of their tetracyclic rings. From these results it is suggested that theta-toxin binds to beta-side of the tetracyclic rings but not to alpha-side. 4. A methylsterol and pentacyclic triterpens with 3-hydroxyl group also inhibited the hemolysis, but steroids and their related compounds either with a hydrophylic or without a hydrophobic group at their ring D had little, if any, inhibitory power.

Chemical Phenomena↗
PubMed1975

Clostridium perfringens exotoxins. III. Binding of theta-toxin to erythrocyte membrane.

When Clostridium perfringens theta-toxin was incubated with sheep erythrocytes the toxin activity disappeared before lysis, the fact of which suggests fixation of the toxin to erythrocyte membranes. 2. Theta-Toxin lost its activity by binding to cell membranes, and the membrane constituted inhibitor of theta-hemolysis was neither a protein, a carbohydrate nor a phosphatide, but was cholesterol. From these results this report proposes that the theta-toxin binding site of erythrocytes should be cholesterol.

Binding Sites↗