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Biomedical subjects

S Miyazaki

Publications and source records attributed to S Miyazaki.

At least 883 records · Page 49Linked to original sources
PubMed1979

[A case of accessory middle cerebral artery associated with internal carotid artery aneurysm (author's transl)].

A case of accessory middle cerebral artery associated with internal carotid artery aneurysm was reported. A 50-year-old female was admitted to our hospital with complaints of headache, nausea, vomiting and conciousness disturbance. Lumbar puncture showed bloody CSF. Right carotid angiogram revealed saccular aneurysm of the internal carotid-posterior communicating artery and accessory middle cerebral artery originating from the horizontal portion of the right anterior cerebral artery. No other vascular lesion was observed on other angiograms. Operation was performed 2 days after admission. The neck of the aneurysm was clipped. Postoperative aseptic meningitis was cured by frequent lumbar punctures, and her course was uneventful. The etiological hypothesis of these cerebral vascular anomalies was briefly discussed.

Carotid Artery Diseases↗
PubMed1978

A model for anomalous rectification: electrochemical-potential-dependent gating of membrane channels.

A model is presented for "anomalous rectification" based upon electrical measurements on the egg cell membrane of the starfish. The objective is to postulate a plausible molecular mechanism which yields an expression for the conductance similar to that deduced empirically by Hagiwara and Takahashi (1974), i.e.,: formula: (see text), where B, deltaVh and v are constant, cK is the external K+ concentration, and deltaV (= V - V0) is the displacement of the membrane potential from its resting value. It is shown that a similar dependence of the conductance on deltaV is expected for a particular class of models in which the K+ ions are also implicated in "gating". To give a specific example, we consider the case in which the formation of ion-permeable pores requires a voltage-induced orientation of membrane-bound, electrically-charged groups and subsequent complexation of these groups with the external cations. Furthermore, the proportionality between GK and CK1/2, when the internal K+ concentration is constant, is accounted for by conventional descriptions of the ionic fluxes using Eyring's rate reaction theory. In terms of the present model, B and deltaVh are explicit functions of the internal K+ concentrations and are thus constant only as long as this is unvaried. The particular value of v required to fit the data (v congruent to 8.4 mV) is rationalized by the assumption that each of the orientable groups carries three negative elementary charges. In addition, the predictions of the present model are compared with those deduced from an alternative viewpoint, which is related to Armstrong's "blocking particle hypothesis", in that the probability for opening and closing of the pore is assumed to depend on whether the pore is occupied or empty. Differences and similarities between the two models, as well as ways to discriminate between them, are discussed.

Animals↗
PubMed1978

Blocking effects of barium and hydrogen ions on the potassium current during anomalous rectification in the starfish egg.

1. The blocking effects of Ba+ and H+ on the inward K current during anomalous rectification of the giant egg membrane of the starfish, Mediaster aequalis, were studied using voltage clamp techniques. 2. External Ba2+ at a low concentration (10--100 micron) suppresses the inward K current; the extent of suppression, expressed as the ratio of currents with and without Ba2+, can be described by a conventional bimolecular adsorption isotherm, K/(K + [Ba2+]o), K being an apparent dissociation constant. 3. The dissociation constant, K, decreases as the membrane potential V becomes more negative and can be expressed by K(V) = K(0) exp (zmuFV/RT), where K(0) is the K at V = 0, z is the charge of the blocking ion, and mu is a parameter for the membrane potential dependence of Ba2+ blockage. The value of mu ranges between 0.64 and 0.68. 4. Upon a sudden change in membrane potential the change in the blocking effect of Ba2+ follows first order kinetics; the forward rate constant is membrane-potential-dependent whereas the backward constant is potential-independent. 5. The blocking effect of Ba2+ appears to be independent of the activation of K channels during anomalous rectification. 6. The blocking effect of Ba2+ depends on V alone, in contrast to the activation of the K channel during anomalous rectification which depends on V--VK. 7. In these respects, the effect of Ba2+ is equivalent to the introduction of inactivation into the anomalous rectification. 8. SI2+ and Ca2+ show small but observable blocking effects only at much higher concentrations (about 10--20 mM). 9. The inward K current is suppressed when the external pH is reduced below 6.0. The blocking effect of H+ shows no significant potential dependence. The concentration dependence suggests that three H+ ions simultaneously titrate the acidic groups of each channel (pK = 5.3--5.4). 10. The implications of these results are discussed in terms of molecular models of the potassium channel of anomalous rectification and possible mechanisms of K channel inactivation.

Animals↗
PubMed1978

Experimental models for prevention of graft-versus-host reaction in bone marrow transfusion. II. Inability to prevent graft-versus-host reaction in an H-2 identical combination.

Splenomegaly was strong in the degree and continued for a long period of time in adult F1 hybrids between AKR (H-2k) and C3H/He (H-2k) mice after transfer of spleen cells from normal C3H/He mice. In spleen cells of such F1 recipients, cytotoxicity was detected by an in vivo neutralization test using methylcholanthrene-induced sarcoma or AKR origin as target cells. All of newborn F1 recipients died within 17 days after cell transfer. Induction of splenomegaly and cytotoxicity was not prevented by repeated pretreatments of donors with sonicated AKR spleen cells in saline, which suppressed completely such phenomena of graft-versus-host reaction in an H-2 nonidentical combination. Induction of cytotoxicity in the spleen of F1 recipients was not prevented by a pretreatment of donors with AKR spleen cells in complete Freund's adjuvant, which suppressed the induction of cytotoxicity in an H-2 nonidentical combination. Graft-versus-host reaction appears to be stronger in a combination between parental strains of which major histocompatibility antigens were identical.

Animals↗
PubMed1978

Experimental models for prevention of graft-versus-host reaction in bone marrow transfution. III. Reversible and irreversible differentiation of lymphocytes destined for cytotoxicity to effector cells for splenomegaly.

When lymphoid cells were obtained from AKR donors 12 h after a treatment with C57BL/L cells in complete Freund's adjuvant and transferred to (AKR X C57BL/6) F1 mice, splenomegaly in F1 recipients was augmented but cytotoxicity was suppressed. The suppression of cytotoxicity was antigen-specific. When cell transfer was carried out at stages as early as 3 or 6 h after the treatment of donors, cytotoxicity was enhanced but splenomegaly was suppressed. Irreversible deviation of immune response from the generation of cytotoxicity to the development of splenomegaly appears to occur within 12 h after such a treatment of donors.

Bone Marrow Transplantation↗
PubMed1978

Effect of furosemide on urinary kallikrein excretion in patients with essential hypertension.

The effect of furosemide on urinary kallikrein excretion was studied in 10 patients with essential hypertension and 9 normal volunteer subjects. After intravenous administration of furosemide and 2 hours of upright posture, urine volume (UV), urinary sodium (UNaV) and potassium (UKV) excretion, plasma renin activity (PRA), plasma aldosterone concentration (PAC) and urinary kallikrein markedly increased. However, the augmentation of urinary kallikrein in patients with essential hypertension (1.50 +/- 0.19 EU/2 hr) was less remarkable than that in normal subjects (2.33 +/- 0.24 EU/2 hr), although the same degrees of response were observed in PRA and PAC. The increments of UV, UNaV and UKV in patients with essential hypertension were also significantly lower than in normal subjects. Significant positive relations were found between urinary kallikrein and UV or UNaV in both hypertensive and normotensive groups, but there was no such correlation before fursemide administration. It is likely that diuresis and natriuresis induced by furosemide are somehow associated with an increase in urinary kallikrein excretion. Blunted response of urinary kallikrein in essential hypertension may suggest an abnormality in the renal kallikrein-kinin system in this disease.

Adult↗
PubMed1978

Experimental botulism in chickens: the cecum as the site of production and absorption of botulinum toxin.

Highly purified preparations of Clostridium botulinum toxins were administered to chickens by various routes. Chickens were highly susceptible to type A toxin, but relatively resistant to toxins of other types. Type C toxin (12S) at a dose of 1 X 10(7) mouse ip LD50 failed to kill the chicken by the oral route. Oral administration of 10 or more of type A, C, or D spores killed normal chickens, whereas cecoligated chickens were insusceptible to oral administration of 10(6) spores. These results show that the site of production and absorption of botulinum toxin in chickens is the cecum. Peroral administration of spores of a type C strain cured of its prophages and producing the C2 factor only also killed normal chickens. Chickens appeared to the more susceptible to the C2 factor than to the C1 toxin. The C2 factor, therefore, may play more important role in chicken deaths from toxico-infection with type C organisms. The optimum temperature for growth of C. botulinum types C and D was found to be 40-42 C. Type C and D toxins were significantly more stable than type A toxin in the cecum contents with pH above 7. These characteristics and the high density of distribution of type C spores in the environment may explain prevailing cases of type C botulism among broiler chickens.

Animals↗