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Biomedical subjects

H Honjo

Publications and source records attributed to H Honjo.

At least 55 records · Page 3Linked to original sources
PubMed2000

Effect of estrogen and progesterone on gene expression of growth regulatory molecules and proto-oncogene in vascular smooth muscle cells.

We examined influences of estrogen and progestogen on gene expression of the growth regulatory molecules: platelet-derived growth factor (PDGF), interleukin-1 (IL-1), interleukin-6 (IL-6) and proto-oncogene c-myc in vascular smooth muscle cells (VSMC) by reverse transcription-polymerase chain reaction (RT-PCR) and Southern-blotting. VSMC were exposed to estrone-sulfate (E1-S) and medroxyprogesterone acetate (MPA) to induce differentiation. E1-S inhibited the expression of PDGF-A chain, IL-1, IL-6 and c-myc mRNA, whereas MPA had no effect. Inhibition by E1-S was not affected by treatment combined with MPA. These findings suggest that estrogen modulates these growth regulatory molecules and c-myc gene expression in VSMC but not progestogen. We concluded that estrogen may have a direct atheroprotective effect through inhibition of growth regulatory factors.

Arteriosclerosis↗
PubMed2000

Detection and measurement of urinary 2-hydroxyestradiol 17-sulfate, a potential placental antioxidant during pregnancy.

BACKGROUND: Preeclampsia is associated with a quantitative imbalance between lipid peroxide and an antioxidant coproduced in the placenta. To investigate our hypothesis that 2-hydroxyestradiol 17-sulfate (2-OH-ES) is the placental antioxidant during pregnancy, we developed an assay for 2-OH-ES in urine and studied samples from women with and without preeclampsia. METHODS: The detection and measurement of 2-OH-ES in the urine of pregnant women were performed by RIA using highly specific antiserum to 2-OH-ES. To confirm the reliability of the RIA method, the same samples were analyzed by HPLC using an electrochemical detector. RESULTS: Urinary 2-OH-ES values obtained by RIA showed a close relationship to those obtained by HPLC (y = 1.1x - 0.01; r = 0.96). The urinary 2-OH-ES concentrations during the first, second, and third trimesters were 2. 0 +/- 0.6 (mean +/- SE, n = 13), 5.3 +/- 1.3 (n = 21), and 15.3 +/- 2.0 microg/mg creatinine (n = 54), respectively, and <0.15 microg/mg creatinine (n = 10) at 2-24 h after delivery. The concentrations in preeclamptic women during the third trimester were significantly lower, 3.9 +/- 1.9 microg/mg creatinine (mean +/- SE, n = 12). CONCLUSIONS: RIA can be used to measure urinary 2-OH-ES during pregnancy. The increase in urinary 2-OH-ES during gestation, its decrease after delivery, and the lower values in preeclampsia are consistent with a role of 2-OH-ES as a placental antioxidant.

Adolescent↗
PubMed1999

Detection of aromatase cytochrome P-450 in endometrial biopsy specimens as a diagnostic test for endometriosis.

OBJECTIVE: To evaluate the clinical usefulness of examining endometrial biopsy specimens for aromatase cytochrome P-450 as a diagnostic test for endometriosis. DESIGN: Retrospective, case-controlled study. SETTING: Department of Obstetrics and Gynecology, Kyoto Prefectural University of Medicine, Kyoto, Japan. PATIENT(S): One hundred five women of reproductive age with normal menstrual cycles underwent endometrial biopsy laparotomy or laparoscopy, and examination of their tissue revealed endometriosis, adenomyosis, and/or leiomyomas. Patients who had cervical carcinoma in situ but no other gynecologic disease were considered to be disease-free. INTERVENTION(S): Endometrial biopsy specimens were collected. MAIN OUTCOME MEASURE(S): The expression of aromatase cytochrome P-450 was examined by reverse transcription-polymerase chain reaction and immunohistochemical analysis. The distribution and intensity of the immunostaining was assessed using a semiquantitative index designed H-score. RESULT(S): Immunostaining for aromatase cytochrome P-450 was detected in biopsy specimens obtained from patients with endometriosis, adenomyosis, and/or leiomyomas but not in specimens obtained from disease-free patients (H-score <20), with a sensitivity and specificity of 91% and 100%, respectively. CONCLUSION(S): The expression of aromatase cytochrome P-450 in biopsy specimens of eutopic endometrium distinguishes between disease-free women and women with endometriosis, adenomyosis, and/or leiomyomas. This technique can be used at outpatient infertility clinics as an initial screening procedure to rule out the presence of estrogen-dependent disease.

Adult↗
PubMed1999

Arrhythmogenic changes in action potential configuration in the ventricle induced by DC shocks.

Failure of defibrillation by direct current (DC) shocks is the result in part of new ventricular tachyarrhythmias induced by the shocks. We investigated the arrhythmogenic substrate produced by the shocks. Fluorescent action potential (AP) signals were recorded from rabbit hearts perfused in vitro with the use of our original optical recording system. Localized application of 10-ms shocks (S2) during the plateau phase of APs by basic stimuli (S1) caused field intensity (FI)-dependent changes in APs: (a) S2 > 7 V/cm caused additional depolarization, giving rise to a prolongation of AP duration (APD); (b) With S2 > 20 V/cm, terminal repolarization was inhibited, and subsequent postshock S1 APs for 1 to 5 min were characterized by decreases in the maximum diastolic potential and amplitude of APs; and (c) S2 > 30 V/cm often resulted in a prolonged refractoriness, oscillation of membrane potential leading to ventricular tachycardia or fibrillation (VT/VF). The right ventricle was more susceptible than other regions for the aftereffects of high-intensity shocks. Using an 8-channel recording system, we compared the effect of 10-ms monophasic (M) and 5/5-ms biphasic (B) shocks applied to the whole ventricles with FI of 1 to 20 V/cm at the signal recording sites. B shocks were less potent than M shocks in the FI-dependent action potential duration (APD) prolongation, and in the shock-induced enhancement of APD dispersion. Incidence and duration of VT/VF induced by M shocks were significantly greater than those by B shocks. These findings suggest that DC shocks will cause two types of arrhythmogenic substrate: one induced at sites of high FI, and the other at sites with moderate FI. The former would produce local block or focal repetitive excitation due to prolonged depolarization and oscillation of membrane potential, and the latter circuitous movement of wavefronts through an enhancement of spatial inhomogeneity of repolarization.

Animals↗
PubMed1999

Osteoporosis influences the late period of fracture healing in a rat model prepared by ovariectomy and low calcium diet.

To elucidate the influence of osteoporosis on the fracture healing, we produced a rat osteoporosis model by ovariectomy and by maintaining a low calcium diet; and monitored the healing process radiographically, histologically, and biomechanically for 12 weeks. Radiologic, histologic and biomechanical findings of the fracture areas 6 weeks after making the fractures were almost identical in both the osteoporosis group and the control group. However, 12 weeks after making the fractures, newly generated bones in the osteoporosis group showed histological osteoporotic changes and their bone mineral density on the fracture site decreased. These findings show that estrogen-deficient and low calcium conditions greatly affect the bone in the later period of the healing process, but do not affect remarkably the early healing period. This is clinically important when we consider fracture treatments for patients with osteoporosis due to menopause.

Animals↗
PubMed1999

Leptin directly stimulates aromatase activity in human luteinized granulosa cells.

Leptin, the obese (ob) gene product, is secreted by adipocytes and regulates appetite through interaction with hypothalamic leptin receptors. Leptin may also have a stimulatory effect on reproductive function. Furthermore, leptin receptor mRNA is expressed in the ovary, suggesting a direct effect on its function. The present study examines the direct role of leptin on the oestrogen-producing activity in human luteinized granulosa cells. The cells were obtained from in-vitro fertilization pre-ovulatory follicles, precultured for 24 h in the presence of 5% charcoal-treated serum, and incubated for 48-96 h in a serum-free medium containing recombinant human leptin, follicle stimulating hormone (FSH), and/or insulin-like growth factor-I (IGF-I). A single addition of leptin (0. 5-10 ng/ml) stimulated aromatase activity with the incubation time of up to 96 h. The addition of leptin (1 ng/ml) further augmented the stimulation by a single addition of FSH (100 ng/ml) or IGF-I (100 ng/ml), or a combination of both. A single addition of leptin (1 ng/ml) or a combination of leptin (1 ng/ml), FSH (100 ng/ml), and IGF-I (100 ng/ml) gave rise to an increase in each parameter of oestrogen-producing activity measured, i.e. P450arom mRNA level, P450arom protein level, aromatase specific activity, and the oestradiol concentration in the culture supernatant. However, the production of progesterone did not change. These results indicate that leptin stimulates oestrogen production by increasing P450arom mRNA and P450arom protein expression and, consequently, aromatase activity by its direct action on the human luteinized granulosa cells.

Aromatase↗
PubMed1999

Downward gradient in action potential duration along conduction path in and around the sinoatrial node.

Regional differences in electrical activity in rabbit sinoatrial node have been investigated by recording action potentials throughout the intact node or from small balls of tissue from different regions. In the intact node, action potential duration was greatest at or close to the leading pacemaker and declined markedly in all directions from it, e.g., by 74 +/- 4% (mean +/- SE, n = 4) to the crista terminalis. Similar data were obtained from the small balls. The gradient is down the conduction pathway and will help prevent reentry. In the intact node, a zone of inexcitable tissue with small depolarizations of <25 mV or stable resting potentials was discovered in the inferior part of the node, and this will again help prevent reentry. The intrinsic pacemaker activity of the small balls was slower in tissue from more inferior (as well as more central) parts of the node [e.g., cycle length increased from 339 +/- 13 ms (n = 6) to 483 +/- 13 ms (n = 6) in transitional tissue from more superior and inferior sites], and this may help explain pacemaker shift.

Action Potentials↗
PubMed1999

Regional differences in effects of E-4031 within the sinoatrial node.

Effects of block of the rapid delayed rectifier K+ current (IK,r) by E-4031 on the electrical activity of small ball-like tissue preparations from different regions of the rabbit sinoatrial node were measured. The effects of partial block of IK,r by 0.1 microM E-4031 varied in different regions of the node. In tissue from the center of the node spontaneous activity was generally abolished, whereas in tissue from the periphery spontaneous activity persisted, although the action potential was prolonged, the maximum diastolic potential was decreased, and the spontaneous activity slowed. After partial block of IK,r, the electrical activity of peripheral tissue was more like that of central tissue under normal conditions. One possible explanation of these findings is that the density of IK,r is greater in the periphery of the node; this would explain the greater resistance of peripheral tissue to IK,r block and help explain why, under normal conditions, the maximum diastolic potential is more negative, the action potential is shorter, and pacemaking is faster in the periphery.

Animals↗
PubMed1999

Heterogeneity of 4-aminopyridine-sensitive current in rabbit sinoatrial node cells.

The electrophysiological properties of sinoatrial (SA) node pacemaker cells vary in different regions of the node. In this study, we have investigated variation of the 4-aminopyridine (4-AP)-sensitive current as a function of the size (as measured by the cell capacitance) of SA node cells to elucidate the ionic mechanisms. The 10 mM 4-AP-sensitive current recorded from rabbit SA node cells was composed of transient and sustained components (Itrans and Isus, respectively). The activation and inactivation properties [activation: membrane potential at which conductance is half-maximally activated (Vh) = 19.3 mV, slope factor (k) = 15.0 mV; inactivation: Vh = -31.5 mV, k = 7.2 mV] as well as the density of Itrans (9.0 pA/pF on average at +50 mV) were independent of cell capacitance. In contrast, the density of Isus (0.97 pA/pF on average at +50 mV) was greater in larger cells, giving rise to a significant correlation with cell capacitance. The greater density of Isus in larger cells (presumably from the periphery) can explain the shorter action potential in the periphery of the SA node compared with that in the center. Thus variation of the 4-AP-sensitive current may be involved in regional differences in repolarization within the SA node.

4-Aminopyridine↗
PubMed1999

Expression of aromatase cytochrome P450 in eutopic endometrium and its application as a diagnostic test for endometriosis.

Endometriotic implants, like other estrogen-dependent tumors, contain both estrogen receptors and aromatase cytochrome P450 (P450arom), suggesting that at a local level, endometriotic implants produce estrogens, which may be involved in tissue growth through interaction with the estrogen receptors. P450arom is also expressed in the eutopic endometria of patients with endometriosis, adenomyosis, and/or leiomyomas, whereas neither P450arom protein nor mRNA is expressed in the eutopic endometria of normal menstruating women with cervical carcinoma in situ yet showing no other gynecological disease (disease-free). Examination of P450arom expression in endometrial biopsy specimens enables the physician to discriminate between the presence and absence of endometriosis, and may be used as an initial screening at outpatient infertility clinics. Copyrightz1999S.KargerAG,Basel

Adult↗
PubMed1999

Levels of 24,25-dihydroxyvitamin D3, 25-hydroxyvitamin D3 and 25-hydroxyvitamin D3 3-sulphate in human plasma.

The concentrations of (24R)-24,25-dihydroxyvitamin D3[24,25(OH)2D3], 25-hydroxyvitamin D3[25(OH)D3] and its 3-sulphate [25(OH)D3(3)S] in the plasma of healthy subjects, patients with chronic renal failure, patients with climacteric syndrome, pregnant women and foetuses were determined using the enzyme-linked immunosorbent assay and high-performance liquid chromatography. 25(OH)D3(3)S was not detected in about one-third of the plasma samples from patients with chronic renal failure (n = 26). The three metabolites in maternal plasma reached the highest levels in the second trimester of pregnancy followed by a decrease to the values obtained in the first trimester. Older healthy women (age range 44-71 years) showed higher levels of 24,25(OH)2D3 and 25(OH)D3 in the plasma than did young healthy women (age range 21-29 years), whereas no clear difference was observed between the older healthy women and patients with climacteric syndrome. The level of 25(OH)D3(3)S in the plasma was higher in the latter patients than in healthy women.

24,25-Dihydroxyvitamin D 3↗
PubMed1999

Connexin45, a major connexin of the rabbit sinoatrial node, is co-expressed with connexin43 in a restricted zone at the nodal-crista terminalis border.

The pacemaker of the heart, the sinoatrial (SA) node, is characterized by unique electrical coupling properties. To investigate the contribution of gap junction organization and composition to these properties, the spatial pattern of expression of three gap junctional proteins, connexin45 (Cx45), connexin40 (Cx40), and connexin43 (Cx43), was investigated by immunocytochemistry combined with confocal microscopy. The SA nodal regions of rabbits were dissected and rapidly frozen. Serial cryosections were double labeled for Cx45 and Cx43 and for Cx40 and Cx43, using pairs of antibody probes raised in different species. Dual-channel scanning confocal microscopy was applied to allow simultaneous visualization of the different connexins. Cx45 and Cx40, but not Cx43, were expressed in the central SA node. The major part of the SA nodal-crista terminalis border revealed a sharply demarcated boundary between Cx43-expressing myocytes of the crista terminalis and Cx45/Cx40-expressing myocytes of the node. On the endocardial side, however, a transitional zone between the crista terminalis and the periphery of the node was detected in which Cx43 and Cx45 expression merged. These distinct patterns of connexin compartmentation and merger identified suggest a morphological basis for minimization of contact between the tissues, thereby restricting the hyperpolarizing influence of the atrial muscle on the SA node while maintaining a communication route for directed exit of the impulse into the crista terminalis.

Animals↗
PubMed1999

Serum 2-hydroxyestradiol 17-sulphate in pregnancy.

2-Hydroxyestradiol 17-sulphate (2-OH E2-17-S) is a catecholized form of sulphated estrogen. In vitro studies showed that its antioxidative effect is almost equal to that of free catecholestrogens, such as 2-OH E2 or 4-OH E2 and alpha-tocoferol, but the existance of 2-OH E2-17-S in human serum has not yet been made clear. 2-OH E2-17-S strongly antagonizes lipid peroxidation, and so it may play an important role in pregnancy, for example as an anti-oxidant in pregnancy-induced hypertension (PIH). The serum level of 2-OH E2-17-S was measured during mid to late pregnancy by a direct radioimmunoassay (RIA) without hydrolysis. The serum levels at 28-31 weeks, 32-35 weeks and 36-40 weeks of gestation were 4.68+/-0.93 (mean+/-SE), 8.38+/-1.21 and 18.31+/-3.41 nmol/l, respectively. The serum level in PIH cases at 36-40 weeks (4.64+/-1.29 nmol/l) was significantly lower than that in normal pregnancy. The 2-OH E2-17-S level in umbilical arteries was significantly higher than that in maternal peripheral vein. These results suggest that the feto-placental unit plays an important role in catecholizing E2-17-S to 2-OH E2-17-S, which may act as an antioxidant in pregnancy.

Estradiol↗
PubMed1999

[Efficacy of hormone replacement therapy on hyperlipidemia].

In women, serum lipid levels and the incidence of myocardial ischemia increase after menopause. Deficiency of estrogen is believed to be the cause of these epidemiological phenomena. On the other hand, hormone replacement therapy(HRT), has prevailed in developed countries. Estrogen is replaced to ease climacteric disorders, and retard bone loss. Many clinical studies cleared the effect of HRT on lipids, in which total and LDL-C (cholesterol) decreased, and HDL-C increased. TG increased by conjugated equilin estrogen but not by transdermal estradiol. In our study, hepatic triglyceride lipase(HTGL) was suppressed by HRT, but lipoprotein lipase(LpL) was not suppressed. HRT decreases coronary artery diseases, but it is still controversial whether HRT is efficient in patients who already have heart disease.

Coronary Artery Disease↗
PubMed1998

Na+ channel blocking effects of cibenzoline on guinea-pig ventricular cells.

The effects of cibenzoline on transmembrane action potentials were examined in right ventricular papillary muscles and in single ventricular myocytes isolated from guinea-pig hearts. In papillary muscles, cibenzoline > or = 3 microM caused a significant decrease in the maximum upstroke velocity (Vmax) of the action potential without affecting the action potential duration. The inhibition of Vmax was enhanced at higher stimulation frequencies. In the presence of cibenzoline, trains of stimuli at rates > or = 0.2 Hz led to a use-dependent inhibition of Vmax. The time constant for Vmax recovery (tauR) from the use-dependent block was 26.2 s. The use-dependent block of Vmax with cibenzoline was enhanced and tauR was shortened when the resting potential was depolarized by high (8, 10 mM) [K+]o. The curve relating membrane potential and Vmax in single myocytes was shifted by cibenzoline (10 microM) in a hyperpolarizing direction by 7.1 mV. In myocytes treated with cibenzoline (10 microM), a 10-ms conditioning clamp to 0 mV caused a significant decrease in Vmax of the subsequent test action potential; the Vmax inhibition was enhanced modestly in association with a prolongation of the 0 mV clamp pulse duration. In the presence of cibenzoline (3 microM), application of a train of depolarizing pulses (10 ms, 200 ms) to myocytes from the resting level (-80 mV) to 0 mV resulted in a progressive Vmax reduction in a pulse number-dependent manner. Unlike glibenclamide (30 microM), cibenzoline (10 microM) did not prevent the hypoxia-induced shortening of action potential duration in papillary muscles. These findings indicate that the onset and offset kinetics of use-dependent Na+ channel block by cibenzoline are slow. Given its state dependence, cibenzoline may be a blocker of activated Na+ channels. The inhibitory action of this compound on the ATP-sensitive K+ current (I(K), ATP) would be minimal or negligible at concentrations causing sufficient Na+ channel block.

Animals↗
PubMed1998

Low-frequency extracellular potentials recorded from the sinoatrial node.

OBJECTIVE: To study the morphology of small extracellular potentials localized to the sinoatrial (SA) node and to elucidate its potential usefulness in evaluating SA node dysfunction. METHODS: Extracellular potentials were recorded from the endocardial surface of the SA node in isolated right atrial preparations of rabbits through custom-made modified bipolar electrodes with high-gain amplification and a low-frequency (0.5-32 Hz) filter setting. RESULTS: The potentials in and around the SA node under control conditions showed a variety of morphologies. In a small area near the leading pacemaker site, slow primary negative deflections were preceded by a gradual increase of the negativity (73.5 +/- 5.6 microV in amplitude, n = 12). In the periphery of the SA node cranial and caudal to the leading pacemaker site, slow positive/negative deflections were recorded. In the septal side of the SA node showing very slow conduction, the electrograms showed slow primary positive deflections. Transient pacemaker shifts induced by atrial stimulation or vagal nerve stimulation were reflected well in morphologies of the extracellular potentials. In the presence of 20 microM TTX, wide and slow negative deflections were observed in the center and periphery of the SA node in association with extremely slow conduction restricted to a corridor-like area along the crista terminalis, whereas the atrial muscle surrounding the area was made inexcitable. In the presence of 1 microM nifedipine, the leading pacemaker site was shifted to the periphery of the SA node close to the crista terminalis. The negative deflection in the center and septal side of the SA node disappeared reflecting no excitation of the area. CONCLUSION: The endocardial extracellular electrograms recorded in and around the SA node under appropriate conditions reflect two dimensional activation sequences. They would provide useful information in recognizing the leading pacemaker site and alterations of the conductivity and excitability.

Animals↗
PubMed1998

Expression of exon 5 deleted estrogen receptor variant messenger RNA in human uterine myometrium and leiomyoma.

To examine the relationship between uterine leiomyoma, an estrogen-dependent tumor and its estrogen receptor, the relative amounts of wild type estrogen receptor (WT) mRNA and exon 5 deleted estrogen receptor variant (D5-ER) mRNA to G3PDH mRNA were examined in human uterine myometrium and leiomyoma specimens obtained from 46 patients in 3 age groups (group A: 41-45 years old, group B: 46-50 years old, group C: 51-54 years old) using a quantitative reverse transcription polymerase chain reaction method (RT-PCR). D5-ER mRNA was co-expressed with WT mRNA in all myometrium and leiomyoma specimens. In myometrium, the relative amount of WT decreased with aging, but in leiomyoma, it was high in group B. The relative amount of D5-ER mRNA and the ratio of D5-ER mRNA to WT mRNA (D5/WT ratio) were significantly higher in group C in both myometrium and leiomyoma. The percentage of the patients whose D5/WT ratio was higher in leiomyoma than in myometrium (L/M ratio>1.0) increased with age. These findings suggest that D5-ER increases to supplement the decreasine in WT in uterine tissues toward menopause and that D5-ER plays a more active role in leiomyoma than in myometrium during the perimenopausal period.

Adult↗