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Makoto Sakai

Publications and source records attributed to Makoto Sakai.

17 recordsLinked to original sources
PubMed2006

Bio-photosensor: Cyanobacterial photosystem I coupled with transistor via molecular wire.

We report on the first successful output of electrons directly from photosystem I (PSI) of thermophilic cyanobacteria to the gate of a field-effect transistor (FET) by bypassing electron flow via a newly designed molecular wire, i.e., artificial vitamin K(1), and a gold nanoparticle; in short, this newly manufactured photosensor employs a bio-functional unit as the core of the device. Photo-electrons generated by the irradiation of molecular complexes composed of reconstituted PSI on the gate were found to control the FET. This PSI-bio-photosensor can be used to interpret gradation in images. This PSI-FET system is moreover sufficiently stable for use exceeding a period of 1 year.

Biosensing Techniques↗
PubMed2005

Excited state hydrogen transfer in fluorophenol.ammonia clusters studied by two-color REMPI spectroscopy.

Two-color (1 + 1') REMPI mass spectra of o-, m- and p-fluorophenol.ammonia (1 ration) clusters were measured with a long delay time between excitation and ionization lasers. The appearance of NH(4)(NH(3))(n-1)(+) with 100 ns delay after exciting the S(1) state is a strong indication of generation of long-lived species via S(1). In analogy with the phenol.ammonia clusters, we conclude that an excited state hydrogen transfer reaction occurs in o-, m- and p-fluorophenol.ammonia clusters. The S(1)-S(0) transition of o-, m- and p-fluorophenol.ammonia (1 : 1) clusters were measured by the (1 + 1') REMPI spectra, while larger (1 ration) cluster (n = 2-4) were observed by monitoring the long-lived NH(4)(NH(3))(n-1) clusters action spectra. The vibronic structures of m- and p-fluorophenol.ammonia clusters are assigned based on vibrational calculations in S(0). The o-fluorophenol.ammonia (1 : 1) cluster shows an anharmonic progression that is analyzed by a one-dimensional internal rotational motion of the ammonia molecule. The interaction between the ammonia molecule and the fluorine atom, and its change upon electronic excitation are suggested. The broad action spectra observed for the o-fluorophenol.ammonia (1 : n) cluster (n>== 2) suggest the excited state hydrogen transfer is faster than in m- and p-fluorophenol.ammonia clusters. The different reaction rates between o-, m- and p-fluorophenol.ammonia clusters are found from comparison between the REMPI and action spectra.

Ammonia↗
PubMed2005

Probing stepwise complexation in phenylazomethine dendrimers by a metallo-porphyrin core.

A series of dendritic phenylazomethines (DPA), which have a meso-substituted zinc porphyrin core (DPAGX-ZnP, X = 1-4), were synthesized. Structural studies of these dendrimers were carried out using Tri-SEC (triple detection after size exclusion chromatography), intrinsic viscosity analysis, TEM (tunneling electron microscopy), and molecular modeling calculations by AM1. As a result, a sphere-like structure within a single-nanometer scale (R(h) = 22 A for DPAG4-ZnP) was observed. In addition, encapsulating effects by the DPA shell in the larger dendrimers were confirmed as fundamental properties, based on the UV-vis abosorption spectra, cyclic voltammograms, and 1H NMR spin-lattice relaxation times (T1). The DPAGX-ZnP acts as a multi-metal ion reservoir for SnCl2 and FeCl3. The generation-4 dendrimer (DPAG4-ZnP) can take up to 60 molar amounts of metal complexes around the porphyrin core. A quantitative study of the metal assembling reaction by UV-vis titration revealed stepwise layer-by-layer complexations from the inner imines nearest to the core to the surface. The redox behavior and fluorescence of the zinc porphyrin in these metal-assembled dendrimers also support the stepwise complexation of the metal ion. These analyses suggest that the finely assembled metal complexes in a dendrimer architecture strongly affect the electronic status of the porphyrin core. Results from transient absorption measurements strongly indicate a very fast electron transfer on a subpicosecond time scale between the core and assembled metal complexes.

Azo Compounds↗
PubMed2005

[Effects of reduced dialysate calcium on mineral metabolism in hemodialysis patients].

AIM: To study the effects of decreased dialysis calcium on mineral metabolism. METHODS: Dialysis calcium concentration was switched from 3.0 mEq/L to 2.5 mEq/L. Changes of serum Ca, P, and PTH were monitored for 6 months in 58 hemodialysis patients. RESULTS: Serum calcium decreased 2 weeks after the switch of dialysate, although it returned to the basal level after 6 months because of increased dosage of vitamin D. Phosphorus transiently increased after the switch. I-PTH increased in patients whose i-PTH before the switch was less than 100 pg/mL. PTH decreased in patients whose i-PTH exceeded 300 pg/mL. CONCLUSION: Decreased dialysis calcium produced lower serum calcium and better PTH control.

Calcium↗
PubMed2004

The beneficial effect of effective control of anemia on hyperinsulinemia and hypoxemia in a hemodialysis patient with corrected transposition of the great arteries.

We report the beneficial effect of control of anemia on hyperinsulinemia and hypoxemia in a hemodialysis patient with corrected transposition of the great arteries. The patient's hemoglobin (Hb) level of 10.3 g/dl on admission represents good control for hemodialysis (HD) patients, but it was too low for this patient with secondary polycythemia because of a right-to-left shunt. Control of anemia for a 10-month period was followed by a marked increase in Hb level (from 10.3 g/dl to 13.9 g/dl) and in aerobic work capacity, while the fasted insulin level decreased from 36.7 microU/ml to 8.0 microU/ml, without changes in leptin level, body mass index (BMI), fat mass, Kt/V, or protein catabolic rate (PCR). Additionally, hypoxemia was ameliorated, from PO2 33.1 mmHg to PO2 56.2 mmHg, and the hyperdynamic cardiac state was improved. The degree of anemia, together with deteriorating tissue oxygenation, may have predisposed this patient to developing insulin resistance and consequent hyperinsulinemia. The most appropriate target Hb concentration should be tailored for the clinical condition of each individual patient, bearing in mind an insulin-resistance state, especially in hemodialysis patients with hypoxemia. A more complete understanding of what regulates insulin resistance and consequent hyperinsulinemia in endstage renal disease (ESRD) awaits the elucidation of carbohydrate and insulin metabolism.

Adult↗
PubMed2004

Effect of bullfrog LH and FSH on newt testes under different temperatures.

Environmental temperature plays important roles for amphibian gonadal function. In this study, we examined the responses of testicular tissue of adult male newts (Cynops pyrrhogaster) to amphibian gonadotropins both in vitro and in vivo under different temperatures. When minced testes were incubated in vitro at different temperatures (8-37 degrees C) under an atmosphere of 95% O(2)-5% CO(2) for 3h with bullfrog luteinizing hormone (LH) or follicle-stimulating hormone (FSH), LH stimulated testosterone production more than FSH. The testosterone production increased as the incubation temperature increased. Hypophysectomized newts were injected with bullfrog LH or FSH and maintained at 8 or 18 degrees C. In the 18 degrees C group, the testicular weight of the hypophysectomized control decreased when compared with that of with the intact control. The testicular weight of the LH-treated hypophysectomized group decreased more than that of the hypophysectomized control, indicating that LH induced the evacuation of mature spermatozoa from the testes of LH-treated hypophysectomized newts. In the FSH-treated newts, the testicular weight was greater than that in the hypophysectomized control, and was maintained at a value similar to that of the intact control. In the 8 degrees C group, there was no significant difference in testicular size among the intact control, hypophysectomized control, and FSH-treated newts. LH strongly induced spermiation as it did at 18 degrees C. The plasma testosterone level in the hypophysectomized newts decreased dramatically, but LH was effective in restoring it. Its effect was more potent at 8 degrees C than at 18 degrees C. On the other hand, FSH did not induce a significant increase in the plasma testosterone levels at either temperatures. The results indicate a temperature-dependent difference in responsiveness of the testis both in vitro and in vivo to LH and FSH.

Animals↗
PubMed2004

Bio-intact parathyroid hormone and intact parathyroid hormone in hemodialysis patients with secondary hyperparathyroidism receiving intravenous calcitriol therapy.

Intact parathyroid hormone (iPTH) assay has been the most widely used for the diagnosis of secondary hyperparathyroidism and evaluation of vitamin D therapy. However, 1-84 PTH assay might be a better diagnostic tool since iPTH detects not only 1-84 PTH but also large C-terminal fragments, which would antagonize PTH action. Therefore, we conducted a multicenter study to evaluate the clinical usefulness of a newly developed immunochemiluminometric assay for 1-84 PTH, Bio-Intact PTH (BiPTH). Thirty-five uremic patients with secondary hyperparathyroidism participated in the study. Intravenous calcitriol therapy was continued for 12 months. iPTH and bone-specific alkaline phosphatase (BAP) were monitored at each dialysis center to control the dose of calcitriol. Serum and plasma samples were collected from each center and both iPTH and BiPTH were measured using Allegro-Lite assay reagents from Nichols Institute Diagnostics (San Clemente, CA, USA). Intravenous calcitriol suppressed iPTH after 1 month as well as BiPTH. Bone-specific alkaline phosphatase decreased after 3 months. A high degree of correlation between Nichols iPTH and BiPTH (y = 0.3913 x + 19.517, r = 0.9561) was demonstrated with a BiPTH/iPTH ratio of approximately 0.44. Significant correlation between BAP and iPTH, or between BAP and BiPTH was not observed. Our limited data failed to demonstrate the superiority of BiPTH to iPTH. Therefore, further investigations would be necessary to examine the relationship between BiPTH and bone histomorphometry.

Aged↗
PubMed2003

Deep venous thrombosis, myocardial infarction, and occlusion of vascular access associated with heparin-induced thrombocytopenia in a diabetic hemodialysis patient.

We report a patient with diabetic endstage renal disease with an initial platelet count of 17.6 x 10(4)/mm3 who developed type-II heparin-induced thrombocytopenia (HIT) during the induction period of hemodialysis (HD) when unfractionated heparin was used. Because the recognition of the condition and the treatment of this patient with HIT was unsatisfactory, she developed deep venous thrombosis, myocardial infarction, and occlusion of vascular access, at times of platelet counts of 4.1 x 10(4), 7.7 x 10(4), and 6.4 x 10(4)/mm3, respectively, with antibodies to heparin/platelet factor 4 complex. Unfortunately, we misjudged in our belief that the thromboembolic events might be associated with an underlying procoagulant state in diabetic nephrotic syndrome, rather than being associated with the clinical picture of HIT. This case report suggests that the clinician must consider HIT in the differential diagnosis for thromboembolic complications during the induction period of HD, because unfractionated heparin is the major anticoagulant used in HD.

Anticoagulants↗
PubMed2003

Recurrent extrusion of cochlear implant at an interval of 5 years.

OBJECTIVE: To describe two different types of device extrusion occurring in the same patient 1 and 6 years after cochlear implantation and to discuss the relation between the two extrusions and problems of cochlear implantation in patients with chronic suppurative otitis media. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENT AND INTERVENTIONS: The patient was a 52-year-old man with profound hearing loss in the right ear caused by chronic otitis media and deafness in the left ear caused by removal of an acoustic neuroma. Surgery for cleaning the tympanic cavity and reconstruction of the bony canal after previous radical mastoidectomy was performed in the right ear first. One year later, cochlear implantation was performed in this ear. RESULTS: One year after implantation, the anterior edge of the internal device of cochlear implant was exposed along the skin incision. This site was stable after corrective surgery. Five years after this operation, however, the posterior edge of the internal device extruded, accompanied by infection around the device. CONCLUSION: The two extrusions occurred with a long interval in between and at two different sites. The first extrusion occurred along the skin incision, and the second extrusion occurred away from the skin incision with infection around the device. The authors assumed that the first and the second extrusion occurred independently; the first extrusion was caused by insufficient blood supply resulting from scar formation from repeated mastoid operations and by pressure on the skin from the internal and external devices, and the second extrusion was caused by proliferated tissue pushing the device upward and against the skin as a result of chronic middle ear infection. The clinical course indicates that sufficiently long follow-up periods are needed to determine the usefulness of the prevention techniques for cochlear implantation in patients with chronic suppurative otitis media.

Cochlear Implantation↗
PubMed2003

A new therapeutic strategy for streptococcal toxic shock syndrome: a key target for cytokines.

We searched for innovative treatments specifically targeted to the cytokines of three critically ill patients with streptococcal toxic shock syndrome (STSS). Direct hemoperfusion with polymyxin B-immobilized fiber improved the hemodynamics in all three patients who had developed shock at presentation. Continuous hemodiafiltration coupled with plasma exchange for simultaneous removal of several mediators of the inflammatory cascade improved outcome in case 2 and lessened the aggressive clinical course and prolonged survival in case 3. The application of these technologies appears to open new and interesting therapeutic options and may lead to improved survival in STSS.

Adult↗
PubMed2002

[Effects of fentanyl on acetylcholine release from hippocampus and righting reflex in rat: an in vivo brain microdialysis study].

Fentanyl, a synthetic mu-opioid agonist, is one of the most popular opioids in clinical anesthesia. It is well-known that memory is affected by opioids and opioid antagonists in animals. Cholinergic neurones releasing acetylcholine (ACh) particularly in the hippocampus have been shown to be related to memory. This study, therefore, was conducted to examine the effects of fentanyl on hippocampal ACh release in rats. The experiments were performed on male SD rats under freely moving condition by in vivo brain microdialysis technique. After taking initial three samples, test drugs were administered. The ACh release was determined by HPLC-ECD method. Effect on behavior was determined as loss of righting reflex (LRR). Fentanyl 50, 100 and 200 micrograms.kg-1 i.p. significantly decreased the ACh release from the rat hippocampus. Naloxone, a mu-antagonist, 100 micrograms.kg-1 i.p. antagonized the inhibitory effect of fentanyl 100 micrograms.kg-1 i.p. on the ACh release in the hippocampus. Only fentanyl 200 micrograms.kg-1 i.p. produced LRR. The effects of fentanyl, the dose of which is so little that it does not produce LRR, on the rat hippocampal ACh release may be controlled by the inhibitory actions of mu-opioid receptors.

Acetylcholine↗
PubMed2002

Experimental studies on the role of fructose in the development of diabetic complications.

We examined the role of fructose in the development of diabetic complications. Compared with glucose, fructose increased the fluorescence intensity and the cross-linking of glycated collagen, and promoted the polymerization of proteins. Therefore fructose accelerated the production of advanced glycation end-products more than glucose. In addition, fructose enhanced the reactive oxygen or oxygen radical generation and the associated degeneration of proteins and lipids. These actions of fructose appeared to be due to the formation of dicarbonyl compounds such as 3-deoxyglucosone, a highly reactive intermediate product formed in the advanced glycation stage. These results suggest that fructose is closely involved not only in glycation but also in the polyol pathway and peroxidation reactions through free radical formation. Thus, fructose is considered to be a more critical reducing sugar associated with the progression of diabetic complications than it has been thought until now.

Aldehyde Reductase↗