PubMed Health⌕ Search

Biomedical subjects

Y Isogai

Publications and source records attributed to Y Isogai.

At least 37 records · Page 2Linked to original sources
PubMed1996

Parathyroid hormone regulates osteoblast differentiation positively or negatively depending on the differentiation stages.

The effects of parathyroid hormone (1-34) (PTH (1-34) on osteoblast differentiation were investigated using primary osteoblast-like cells isolated from newborn mouse calvaria. The osteoblast-like cells cultured at low cell densities, in which the cells remained in a subconfluent state at the end of culture, were exposed for 7 days to PTH. This stimulated alkaline phosphatase (ALP) activity in a dose-dependent manner. In contrast, PTH dose-dependently inhibited both ALP activity and osteocalcin production in cells inoculated at high cell densities, in which they had reached a confluent state before the end of culture. The changes of ALP activity by PTH were accompanied with the expression of ALP messenger RNA. PTH induced no changes of the hydroxyproline content in the cell layer when the cells were exposed to the hormone at a subconfluent state, but reduced the content at a postconfluent state. The stimulation of ALP activity by PTH at a preconfluent state was retained even after the removal of PTH from the culture media. The opposite effect of PTH, observed between the preconfluent and the postconfluent state, was reproduced by adding dibutyryl cyclic adenosine monophosphate (cAMP) or forskolin, but not by adding phorbol myristate acetate. In a colony-forming unit fibroblastic (CFU-F) assay, using bone marrow cells isolated from tibiae of 10-week-old mice, PTH induced no changes in the total number of CFU-Fs, but increased the proportion of ALP-positive colonies. These results indicate that PTH exerts opposite effects on the phenotypic expression of osteoblasts, depending on their differentiation stages of osteoblasts. PTH may preferentially stimulate osteoblast differentiation in immature osteoblasts but inhibit it in more mature cells.

Alkaline Phosphatase↗
PubMed1996

Calcitonin-induced changes in the cytoskeleton are mediated by a signal pathway associated with protein kinase A in osteoclasts.

Calcitonin is known to inhibit osteoclastic bone resorption through its receptor, which is abundantly expressed on the plasma membrane of osteoclasts. Recently, it was reported that calcitonin receptors were coupled to both cAMP-dependent protein kinase (PKA) and protein kinase C (PKC). To examine how the PKA and PKC pathways are involved in the effects of calcitonin, we focused on changes in the cytoskeleton of murine osteoclast-like multinucleated cells (OCLs) formed in vitro. When OCLs were cultured on dentine slices, they formed resorption pits and ringed structures of F-actin dots (actin rings). Elcatonin, a synthetic analogue of eel calcitonin, disrupted actin rings and inhibited pit formation in a dose-dependent manner. Forskolin and dibutyryl cAMP, both of which have the ability to activate PKA, mimicked the effects of elcatonin. Phorbol myristate acetate and phorbol 12,13-dibutyrate, both of which have the ability to activate PKC, also inhibited pit-forming activity, but little affected actin rings of OCLs. The inhibitory effects of elcatonin on the pit formation and actin ring formation were partially restored by the treatment with Rp-cAMPs, a cAMP antagonist. Elcatonin induced a rapid increase in PKA activity within a few minutes, and its activation by elcatonin occurred in a dose-dependent manner. The time- and dose-dependent profiles of elcatonin for the activation of PKA were similar to those for the disruption of actin rings. Moreover, microinjection of activated PKA into OCLs disrupted actin rings within 10 min on culture dishes. Actin rings were little affected by the microinjection of the PKA preincubated with a cAMP-dependent protein kinase inhibitor (IP-20) into OCLs. These results suggest that PKA activation, rather than PKC activation, is involved in mediating the effects of calcitonin, through the disruption of actin organization.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Resolution of the aerobic respiratory system of the thermoacidophilic archaeon, Sulfolobus sp. strain 7. II. Characterization of the archaeal terminal oxidase subcomplexes and implication for the intramolecular electron transfer.

The terminal segment of the aerobic respiratory chain of the thermoacidophilic archaeon Sulfolobus sp. strain 7 is an unusual caldariellaquinol oxidase supercomplex, which contains at least one b-type and three spectroscopically distinguishable a-type cytochromes, one copper, and a Rieske-type FeS center. In this paper, we report the purification and characterization of two different forms of the archaeal a-type cytochromes, namely, a three-subunit cytochrome a583-aa3 subcomplex and a single-subunit cytochrome aa3 derived from the cytochrome subcomplex, in order to facilitate further studies on the terminal oxidase segment of Sulfolobus. The optical and EPR spectroscopic analyses suggest the presence of two different low-spin heme centers and one high-spin heme center in the purified cytochrome a583-aa3 subcomplex, and one low-spin and one high-spin hemes in cytochrome aa3, respectively. The Rieske-type FeS center detected in the purified cytochrome supercomplex was absent in two forms of the a-type cytochrome oxidase, indicating its association with cytochrome b562. The crystal field parameters of the lowspin heme a583 center indicate that its axial ligands may be similar to those of cytochromes c, rather than conventional bis-histidine ligation. In spite of the absence of any c-type cytochrome, a ferrocytochrome c oxidase activity was detected in the archaeal purified cytochrome a583-aa3 subcomplex with no quinol oxidase activity, but not in the purified cytochrome oxidase supercomplex, which has been tentatively interpreted as a representative of electron transfer from the Rieske FeS center to cytochrome a583 in vivo. Thus, our results indicate the following scheme for the intramolecular electron transfer of the terminal oxidase supercomplex from Sulfolobus sp. strain 7: [caldariellaquinol-->] b562-->Rieske FeS center-->a583 aa3-->molecular oxygen.

Ascorbic Acid↗
PubMed1995

Iron-ligand structure and iron redox property of nitric oxide reductase cytochrome P450nor from Fusarium oxysporum: relevance to its NO reduction activity.

We studied the nitric oxide reductase, cytochrome P450nor, purified from a denitrifying fungus Fusarium oxysporum with electron paramagnetic resonance spectral and redox potential measurements. The EPR spectral features of P450nor in the ferric resting, the ferric cyanide-bound, and the ferrous NO-bound forms were the same as the corresponding ones of other general P450s such as Pseudomonas putida P450cam. In contrast, the metyrapone complex of ferric P450nor gave an EPR spectrum with significantly different g values from that of P450cam. The EPR results were explained in terms of similarity in the immediate configuration of the S(-)-Fe-ligand (H2O, CN-, NO) structure between P450nor and P450cam but a structural difference at the heme distal pocket, especially in the substrate binding domain; P450cam has a camphor binding domain, while P450nor does not. In spite of the same S(-)-Fe-H2O configuration, the redox potential of P450nor in the ferric/ferrous couple was measured to be -307 mV, which is much lower than those of the camphor-bound (-140 mV) and -free (-250 mV) P450cam. The lower redox potential could be attributable to the different electrostatic interaction of the heme with its surroundings; e.g., the heme environment of P450nor is charged either more negatively or less positively than P450cam.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1995

Spectral analyses of R-R interval and systolic blood pressure in diabetic autonomic neuropathy.

We studied autonomic nervous system function using the principle of maximum entropy (ME) to perform spectral analyses of the R-R interval and systolic blood pressure in 32 diabetic patients and 40 healthy controls. The R-R interval and systolic blood pressure were measured using a continuous, noninvasive monitoring system. The power spectra of both the R-R interval (RR) and systolic blood pressure (SYS) were obtained using ME and the areas of two frequency components were measured: a low- (LFC) and a high-frequency component (HFC). The RR-LFC, RR-HFC and SYS-LFC of diabetic patients were significantly smaller than those of healthy controls. The results of the spectral analyses in diabetic patients correlated with neither disease duration nor nephropathy, while the SYS-LFC showed significant correlations with both retinopathy and the delay in median motor nerve conduction velocity. In the mild autonomic neuropathy group, the RR-LFC and SYS-LFC were not differ from those of healthy controls or patients without autonomic neuropathy. However, the RR-HFC was significantly smaller than that of healthy controls or patients without atonomic neuropathy. In the setting of mild diabetic autonomic neuropathy, it was suggested that cardiac parasympathetic dysfunction preceded both alpha and beta sympathetic dysfunction.

Adult↗
PubMed1995

The mechanism of electron donation to molecular oxygen by phagocytic cytochrome b558.

Phagocytic cytochrome b558 is a unique heme-containing enzyme, which catalyzes one electron reduction of molecular oxygen to produce a superoxide anion with a six-coordinated heme iron. To clarify the mechanism of the superoxide production, we have analyzed oxidation-reduction kinetics of cytochrome b558 purified from porcine neutrophils by stopped-flow and rapid-scanning spectroscopy. Reduced cytochrome b558 was rapidly reoxidized by O2 showing spectral changes with clear isosbestic points, which were also observed during the reduction of ferric cytochrome b558 with Na2S2O4 under anaerobic conditions. The single turnover rate for the reaction with O2 linearly depended on the O2 concentration but was not affected by addition of CO. The rate of the reaction decreased with an increase of pH giving a pKa of 9.7. Under complete anaerobic conditions, ferrous cytochrome b558 was oxidized by ferricyanide at a rate faster than by O2. The thermodynamic analysis shows that the enthalpic energy barriers for the reactions of cytochrome b558 are significantly lower when compared to the autoxidation of native and modified myoglobins through the formation of the iron-O2 complex. These findings are most consistent with the electron transfer from the heme to O2 by an outer-sphere mechanism.

Animals↗
PubMed1995

[The effects of insulin and glucose on the utilization of non-esterified fatty acid in the resting rat skeletal muscle].

The present study was undertaken to clarify the effects of insulin and glucose on the utilization of non-esterified fatty acid (NEFA) in the resting rat skeletal muscle using the perfusion technique. The 24hr-starved and non-starved rat hind limbs were perfused for one hour with the perfusion mediums containing 1mM palmitate and various concentrations of glucose and insulin, and sampling was performed to calculate the clearance of NEFA (F value). In the absence of glucose, the F value of the starved rat hind limb was less than that of the non-starved rats, independently of insulin concentrations (0 and 125 microU/ml) in the perfusion medium (p < 0.02). Moreover, there was no influence of insulin on the F value in both the starved and the non-starved groups. In the presence of 13.9mM glucose, there were no statistically significant differences in the F value without insulin between the non-starved and starved groups. However, the F value was increased in the presence of 62.5 or 125 microU/ml insulin, compared with that in the absence of insulin (p < 0.001), although when the insulin concentration was elevated to 500 microU/ml, it was decreased. Both in the non-starved and the starved groups independently of insulin concentrations, the F value in the glucose-added condition was increased, compared with that in the absence of glucose. These results indicated that the utilization of NEFA in the resting rat skeletal muscle was facilitated by the moderate supply of glucose, although it was suppressed by the presence of abundant glucose.

Animals↗
PubMed1995

Intracellular carboxyl esterase activity is a determinant of cellular sensitivity to the antineoplastic agent KW-2189 in cell lines resistant to cisplatin and CPT-11.

KW-2189, a novel antitumor antibiotic belonging to the duocarmycins, possesses marked DNA-binding activity upon activation by carboxyl esterase to its active form, DU-86. Three duocarmycins, KW-2189, DU-86 and duocarmycin SA, were active against the cisplatin (CDDP)-resistant human non-small cell lung cancer cell lines PC-9/CDDP and PC-14/CDDP, and the multidrug-resistant human small cell lung cancer cell line H69/VP. However, HAC2/0.1, a CDDP-resistant human ovarian cancer cell line which is also resistant to CPT-11 because of decreased intracellular activation of CPT-11, was about 12.8-fold more resistant to KW-2189. HAC2/0.1 was not resistant to other duocarmycins as compared to its parental cell line, HAC2. There was no difference between HAC2 and HAC2/0.1 with regard to the intracellular accumulation of KW-2189. Addition of 130 mU/ml of carboxyl esterase to the culture medium did not influence the sensitivity of HAC2 cells to KW-2189. However, the sensitivity of HAC2/0.1 cells to KW-2189 was enhanced to the level of HAC2. These results suggest that HAC2/0.1 is less potent than HAC2 in activating KW-2189. The carboxyl esterase activity of whole-cell and microsomal extracts from HAC2/0.1 was approximately 60% of that from HAC2. The cell-free experiment revealed that KW-2189 bound to DNA more efficiently in the presence of HAC2 than HAC2/0.1 cell extract. It was concluded that decreased intracellular carboxyl esterase activity in HAC2/0.1 cells caused decreased intracellular conversion of KW-2189 to its active form, thus producing resistance to KW-2189. The decreased conversion of CPT-11 to SN-38 in HAC2/0.1 cells might be explained by decreased carboxyl esterase activity.

Antibiotics, Antineoplastic↗
PubMed1995

Changes in gnathosonic and tooth contact characteristics induced by experimental occlusal interferences created using a full-cast double crown.

Occlusal sounds, contact timings and time moments were measured and analysed on 10 subjects onto whom an occlusal interference was created experimentally. A full-cast double crown was unilaterally set on the upper first molar of each subject, then gradually elevated for 0.06, 0.10, 0.20 and 0.30 mm by inserting a pre-calibrated metal folio. Occlusal sound was measured with an analyser designed for the purpose. Timings and time moments were analysed with a T-scan system. All measurements were performed at least 10 times per subject. The results showed that prolonged occlusal sound duration, changes in acoustic signal waveform and increased shift of the centre of effort were observed concomitantly with crown elevation. Differences in these values at 0.06 mm as compared with those at baseline were not statistically significant. This could be explained through a physiological compensation by the periodontal ligament. The differences with baseline were statistically significant from 0.10 mm ongoing. The distribution of occlusal conacts was determined by the use of a newly developed parameter. Referred to as 'Tap Score', the parameter consists of converting contact timings occurring in seven ranges into least-square-based weighted scores. Analysis of the tap score disclosed evident imbalance between the crowned and the non-crowned side starting from 0.10 mm elevation, whereby a forward shift of the major contact point was observed on the non-crowned side. Our study demonstrated that evident changes in gnathosonic and T-scan parameters are likely to occur at a crown elevation within a 0.06-0.10 mm range.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Changes in auditory P300 event-related potentials and brainstem evoked potentials in diabetes mellitus.

To investigate the influence of diabetes mellitus on higher cognitive functions electrophysiologically, we studied auditory P300 event-related potentials (P300) in 40 NIDDM patients, taking into account wave I-V latencies (I-V) in auditory brainstem evoked potentials, clinical parameters and head MRI findings. Compared with 20 controls, diabetics had significantly longer P300 and I-V latencies. P300 latencies in diabetics correlated with neither I-V, HbA1, blood glucose levels, nor disease duration. Of the 13 diabetics investigated neuroradiologically, four had lacunar infarcts with prolonged electrophysiological values. The remaining nine had normal MRI scans, but their physiological parameters were still significantly longer than those of controls. These findings suggest that NIDDM can independently alter higher cognitive and the central auditory pathway functions. Our data also suggest that these alterations occur regardless of the recent metabolic derangement and disease duration. Cerebrovascular ischemia, if present, also appears to contribute in part to cognitive alterations.

Acoustic Stimulation↗
PubMed1995

Sulredoxin: a novel iron-sulfur protein of the thermoacidophilic archaeon Sulfolobus sp. strain 7 with a Rieske-type [2Fe-2S] center.

A novel pink [2Fe-2S] protein has been purified from the cytosol fraction of the thermoacidophilic archaeon Sulfolobus sp. strain 7 (originally named Sulfolobus acidocaldarius 7) and called "sulredoxin." Its absorption, circular dichroism, and electron paramagnetic resonance spectra suggest the presence of a Rieske-type [2Fe-2S] cluster (g-factors of 2.01, 1.91, and 1.79; average g-factor [gav] = 1.90) which is remarkably similar to that of Thermus thermophilus respiratory Rieske FeS protein (J. A. Fee, K. L. Findling, T. Yoshida, R. Hille, G. E. Tarr, D. O. Hearshen, W. R. Dunham, E. P. Day, T. A. Kent, and E. Münck, J. Biol. Chem. 259:124-133, 1984) and distinctively different from those of the plant-type ferredoxins (gav = 1.96). Sulredoxin, which is the first Rieske-type [2Fe-2S] protein isolated from an archaeal species, does not function as an electron acceptor of the cognate 2-oxoacid:ferredoxin oxidoreductase. Whether sulredoxin is derived from the archaeal membrane-bound respiratory Rieske-type FeS center (gy = 1.91) is the subject of further investigation.

Amino Acid Sequence↗
PubMed1995

[Hypocalcemic effect of elcatonin in mouse models for humoral hypercalcemia of malignancy].

To elucidate the effect of calcitonin on humoral hypercalcemia of malignancy (HHM), we studied the effect of elcatonin, a synthetic eel calcitonin analog, on plasma calcium concentration in hypercalcemic nude mice transplanted subcutaneously with FA-6 pancreas cancer cells and hypercalcemic mice produced by continuous infusion of parathyroid hormone-related peptide (PTHrP). Elcatonin proved to exert a potent hypocalcemic effect in either model for hypercalcemia. The effect reached peaks at 2 hr after its administration, and it was no longer detected at 24 hr. The dose-dependent effects of a single administration of elcatonin were studied in the FA-6 tumor-bearing mice: the hypocalcemic effect of elcatonin at 1-2 hr after administration was dose-relatedly augmented. The effect of daily administration of elcatonin was further studied in the FA-6 tumor-bearing mice: 5-Day daily administration of elcatonin was not accompanied by reduction in its hypocalcemic effect. Moreover, it was suggested that higher the efficacy of elcatonin, the higher were the plasma calcium concentrations in the tumor-bearing mice. These results indicated that elcatonin exerts an immediate hypocalcemic effect even on models for acute and severe hypercalcemia such as FA-6 tumor-bearing mice, that this hypocalcemic effect became more potent depending on their elevation of plasma calcium concentration, and that elcatonin exerts a hypocalcemic effect even on a model for hypercalcemia due to PTHrP, a presumable causative substance of HHM.

Animals↗
PubMed1994

Functional and evolutionary implications of a [3Fe-4S] cluster of the dicluster-type ferredoxin from the thermoacidophilic archaeon, Sulfolobus sp. strain 7.

The dicluster-type ferredoxin is a key electron carrier in the cytoplasm of the aerobic and thermoacidophilic archaeon, Sulfolobus sp. strain 7, and contains 1 aspartate and 7 cysteine residues as possible ligands to two FeS clusters. The optical, electron paramagnetic resonance (EPR), and cyclic voltammetric studies suggest the presence of one each of [3Fe-4S]1+,0 (-280 mV) and [4Fe-4S]2+,1+ (-530 mV) clusters in the purified Sulfolobus ferredoxin, and the lower potential [4Fe-4S] center was scarcely reducible by excess dithionite even at pH 9. While the Sulfolobus ferredoxin has been known to function as an electron acceptor of 2-oxoacid:ferredoxin oxidoreductase (Kerscher, L., Nowitzki, S., and Oesterhelt, D. (1982) Eur. J. Biochem. 128, 223-230), it is not known whether one or both of two clusters is reduced during the steady-state turnover of the enzyme. Here we show by combinations of the optical and EPR spectroscopies that only the higher potential [3Fe-4S] cluster is reduced at the physiological pH during the steady-state turnover of the purified 2-oxoacid:ferredoxin oxidoreductase at 50 degrees C. The functional significance and evolutionary implications of the [3Fe-4S] center in dicluster-type ferredoxins are discussed.

Amino Acid Sequence↗
PubMed1994

Insulin sensitivity test using a somatostatin analogue, octreotide (Sandostatin).

To assess the validity of the steady-state plasma glucose (SSPG) method using octreotide (Sandostatin), we compared the SSPG method with the euglycemic hyperinsulinemic clamp technique in ten non-obese, insulin-dependent diabetic patients. The SSPG method was performed by intravenous infusion of octreotide (0.5 microgram/min), insulin (2 mU/kg/min) and glucose (9 mg/kg/min) for 180 min. Octreotide suppressed endogenous growth hormone, glucagon and insulin secretion. A steady state condition was reached by 90 min, and the mean value of SSPG at 150 and 180 min was used as the index of insulin sensitivity. The euglycemic hyperinsulinemic clamp technique was performed with an artificial endocrine pancreas (Biostator), and insulin sensitivity was expressed as the glucose disposal rate (GDR) from 150-180 min. There was a significant correlation (r = 0.91, p < 0.001) between the results of the two methods. In conclusion, measurement of SSPG, using octreotide to suppress endogenous insulin secretion, is a reliable method to assess insulin sensitivity in man.

Adult↗
PubMed1994

Effect of insulin on sodium reabsorption in hypertensive patients.

The effect of insulin on sodium reabsorption was studied with the hyperinsulinemic euglycemic clamp technique, using lithium clearance as a marker of sodium reabsorption in the proximal tubule. The subjects were 12 nondiabetic hypertensive patients who were divided into two groups. In the first group, the effect of insulin on sodium and lithium reabsorption was examined. The second group served as a control. Blood glucose was continuously monitored from 9 AM to 10 AM (baseline period). Hyperinsulinemic euglycemic clamp was performed with an artificial endocrine pancreas by infusing insulin at a rate of 2 mU/kg.min from 10 AM to noon. In the control group the protocol was exactly the same except that glucose clamp was not performed. Urine was collected hourly from 9 AM to noon. In the glucose clamp group, urinary sodium excretion (UNaV) decreased by 42% during the second hour of the glucose clamp (P < .02). Clearance of lithium (CLi) and fractional distal sodium reabsorption [(CLi-CNa)/CLi] increased, and CNa/CLi decreased significantly during the glucose clamp. In the control group, UNaV and (CLi-CNa)/CLi remained unchanged, and CLi decreased significantly. As shown by the increase of CLi and (CLi-CNa/CLi, and the decrease of UNaV and CNa/CLi in the glucose clamp group, insulin decreases urinary sodium excretion by increasing distal sodium reabsorption, whereas it inhibits sodium reabsorption in the proximal tubule.

Absorption↗
PubMed1994

Comparison of effects of nicardipine and trichlormethiazide on insulin sensitivity in hypertensive patients.

We performed a randomized, crossover study comparing the effects of nicardipine and trichlormethiazide on insulin sensitivity in 8 untreated essential hypertensive patients. They were treated either with nicardipine or trichlormethiazide for 12 weeks, after which they were treated with the alternative drug for a further 12 weeks. Insulin sensitivity was determined by the hyperinsulinemic euglycemic clamp technique. Nicardipine had no adverse effect on insulin sensitivity. Trichlormethiazide decreased insulin sensitivity index by 12%. As nicardipine does not have an adverse effect on insulin sensitivity, it should be preferred in patients who have a proven metabolic abnormality.

Adult↗