Search PubMed⌕ Search

Biomedical subjects

H Honjo

Publications and source records attributed to H Honjo.

At least 19 recordsLinked to original sources
PubMed2006

Involvement of reduced sensitivity to Ca in beta-adrenergic action on airway smooth muscle.

BACKGROUND: It is well known that beta-adrenoceptor agonists (beta-agonists) cause relaxation in airway smooth muscle mediated by a reduction in the concentration of intracellular Ca2+ ([Ca2+](i)). However, little is currently known regarding whether reduced sensitization to Ca2+ is involved in the beta-adrenergic relaxation. OBJECTIVE: This study was designed to determine the intracellular mechanisms underlying suppression of Ca2+ sensitization in beta-adrenergic relaxation (Ca(2+)-independent relaxation by beta-agonists). Methods Isometric tension and [Ca2+](i) were simultaneously measured in fura-2-loaded strips isolated from guinea-pig tracheal smooth muscles. The relationships between tension and [Ca2+](i) were examined in the inhibitory action of isoprenaline (ISO) and other cAMP-related agents against methacholine-induced contraction. RESULTS: The concentration-inhibition curve for ISO against methacholine in tension was significantly dissociated from the curve for ISO in [Ca2+](i). In ISO-induced relaxation, a reduction in tension was significantly greater than that in [Ca2+](i.) This phenomenon was mimicked by other cAMP-related agents: forskolin and dibutyryl-cAMP. In contrast, the inhibitory action of SKF-96365, a non-selective inhibitor of Ca(2+) channels, was associated with that in [Ca2+](i). In the presence of Rp-cAMPS, an inhibitor of protein kinase A (PKA), ISO caused an equivalent relaxation with less reduction in [Ca2+](i). The effects of ISO were not affected by Y-27632, an inhibitor of Rho-kinase, or by bisindolylmaleimide, an inhibitor of protein kinase C. ISO failed to inhibit contraction elicited by calyculin A, an inhibitor of myosin phosphatase. Conclusion beta-Adrenergic action antagonizes not only Ca2+ mobilization but also Ca2+ sensitization in methacholine-induced contraction. The cAMP/PKA-independent, G(s)-direct action is more potent in Ca(2+)-independent relaxation by beta-agonists than the cAMP/PKA-dependent pathway. Moreover, myosin phosphatase is a fundamentally affected protein in the reduced response to Ca2+ mediated by beta-agonist. Our results may provide evidence that this Ca2+ desensitization is a novel target for a reliever medication using rapid-acting beta-agonists in acute asthma management.

Adrenergic beta-Agonists↗
PubMed2006

Connexins in the sinoatrial and atrioventricular nodes.

The sinoatrial node (SAN) and the atrioventricular node (AVN) are specialized tissues in the heart: the SAN is specialized for pacemaking (it is the pacemaker of the heart), whereas the AVN is specialized for slow conduction of the action potential (to introduce a delay between atrial and ventricular activation during the cardiac cycle). These functions have special requirements regarding electrical coupling and, therefore, expression of connexin isoforms. Electrical coupling in the center of the SAN should be weak to protect it from the inhibitory electrotonic influence of the more hyperpolarized non-pacemaking atrial muscle surrounding the SAN. However, for the SAN to be able to drive the atrial muscle, electrical coupling should be strong in the periphery of the SAN. Consistent with this, in the center of the SAN there is no expression of Cx43 (the principal connexin of the working myocardium) and little expression of Cx40, but there is expression of Cx45 and Cx30.2, whereas in the periphery of the SAN Cx43 as well Cx45 is expressed. In the AVN, there is a similar pattern of expression of connexins as in the center of the SAN and this is likely to be in large part responsible for the slow conduction of the action potential.

Action Potentials↗
PubMed2005

Computer three-dimensional reconstruction of the sinoatrial node.

BACKGROUND: There is an effort to build an anatomically and biophysically detailed virtual heart, and, although there are models for the atria and ventricles, there is no model for the sinoatrial node (SAN). For the SAN to show pacemaking and drive atrial muscle, theoretically, there should be a gradient in electrical coupling from the center to the periphery of the SAN and an interdigitation of SAN and atrial cells at the periphery. Any model should include such features. METHODS AND RESULTS: Staining of rabbit SAN preparations for histology, middle neurofilament, atrial natriuretic peptide, and connexin (Cx) 43 revealed multiple cell types within and around the SAN (SAN and atrial cells, fibroblasts, and adipocytes). In contrast to atrial cells, all SAN cells expressed middle neurofilament (but not atrial natriuretic peptide) mRNA and protein. However, 2 distinct SAN cell types were observed: cells in the center (leading pacemaker site) were small, were organized in a mesh, and did not express Cx43. In contrast, cells in the periphery (exit pathway from the SAN) were large, were arranged predominantly in parallel, often expressed Cx43, and were mixed with atrial cells. An approximately 2.5-million-element array model of the SAN and surrounding atrium, incorporating all cell types, was constructed. CONCLUSIONS: For the first time, a 3D anatomically detailed mathematical model of the SAN has been constructed, and this shows the presence of a specialized interface between the SAN and atrial muscle.

Animals↗
PubMed2003

Sarcoplasmic reticulum Ca2+ release is not a dominating factor in sinoatrial node pacemaker activity.

Recent work on isolated sinoatrial node cells from rabbit has suggested that sarcoplasmic reticulum Ca2+ release plays a dominant role in the pacemaker potential, and ryanodine at a high concentration (30 micromol/L blocks sarcoplasmic reticulum Ca2+ release) abolishes pacemaking and at a lower concentration abolishes the chronotropic effect of beta-adrenergic stimulation. The aim of the present study was to test this hypothesis in the intact sinoatrial node of the rabbit. Spontaneous activity and the pattern of activation were recorded using a grid of 120 pairs of extracellular electrodes. Ryanodine 30 micromol/L did not abolish spontaneous activity or shift the position of the leading pacemaker site, although it slowed the spontaneous rate by 18.9+/-2.5% (n=6). After ryanodine treatment, beta-adrenergic stimulation still resulted in a substantial chronotropic effect (0.3 micromol/L isoproterenol increased spontaneous rate by 52.6+/-10.5%, n=5). In isolated sinoatrial node cells from rabbit, 30 micromol/L ryanodine slowed spontaneous rate by 21.5+/-2.6% (n=13). It is concluded that sarcoplasmic reticulum Ca2+ release does not play a dominating role in pacemaking in the sinoatrial node. The full text of this article is available at http://www.circresaha.org.

Action Potentials↗
PubMed2003

Expression of nuclear factor of activated T cells mRNA in maternal peripheral blood cells.

PROBLEM: In T lymphocytes, nuclear factor of activated T cells (NF-AT) regulates the induction of cytokine genes upon antigenic stimulation. This study was designed to analyse the relationship between NF-AT and pregnancy. METHOD OF STUDY: With informed consent, peripheral blood cells (PBCs) were obtained from non-pregnant (n = 114), pregnant (n = 604), and puerperal women (n = 52). The expression of NF-AT2 and NF-AT3 mRNAs in PBCs was measured by a quantitative reverse transcriptase-polymerase chain reaction method. RESULTS: In the early pregnancy period, in successful pregnancy, both NF-AT2 and NF-AT3 mRNAs increased significantly, whereas in cases of spontaneous abortion they did not change significantly. After peaking, they decreased gradually and were re-elevated in the ninth and tenth gestational month. In the puerperal period, NF-AT3 mRNAs decreased, but NF-AT2 mRNA showed a comparatively high expression level. CONCLUSION: These findings suggested that in humans NF-AT signal transduction might be involved in alloantigenic recognition and tolerance and play important roles, especially in the early and late period of pregnancy.

Actins↗
PubMed2002

Endometriosis: the pathophysiology as an estrogen-dependent disease.

Endometriosis, defined as the presence of endometrial glands and stroma outside of the uterine cavity, develops mostly in women of reproductive age and regresses after menopause or ovariectomy, suggesting that the growth is estrogen-dependent. Indeed, the lesions contain estrogen receptors (ER) as well as aromatase, an enzyme that catalyses the conversion of androgens to estrogens, suggesting that local estrogen production may stimulate the growth of lesions. The expression patterns of ER and progesterone receptors in endometriotic lesions are different from those in the eutopic endometrium. Moreover, estrogen metabolism, including the expression pattern of aromatase and the regulation of 17 beta-hydroxysteroid dehydrogenase type 2 (an enzyme responsible for the inactivation of estradiol to estrone), is altered in the eutopic endometrium of women with endometriosis, adenomyosis, and/or leiomyomas compared to that in the eutopic endometrium of women without disease. Immunostaining for P450arom in endometrial biopsy specimens diagnosed these diseases with sensitivity and specificity of 91 and 100%, respectively. This is applicable to the clinical diagnosis of endometriosis. The polymorphisms in the ER-alpha gene, the CYP19 gene encoding aromatase, and several other genes are associated with the risk of endometriosis. Studies of these will lead to better understandings of the etiology and pathophysiology of endometriosis.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

Heterogeneous expression of the delayed-rectifier K+ currents i(K,r) and i(K,s) in rabbit sinoatrial node cells.

1. The electrical activity of sinoatrial node cells is heterogeneous. To understand the reasons for this, the density of the delayed-rectifier K+ current and its two components, i(K,r) and i(K,s), as a function of the size (as measured by cell capacitance) of rabbit sinoatrial node cells was investigated using the whole-cell voltage-clamp technique at 35 degrees C. 2. i(K,r) and i(K,s) were isolated using E-4031 and 293B. Features of the E-4031-sensitive and 293B-insensitive currents corresponded well to those of i(K,r), while features of the E-4031-insensitive and 293B-sensitive currents corresponded well to those of i(K,s). 3. The densities of the outward current under control conditions and the drug-sensitive and -insensitive currents were significantly (P < 0.01) correlated with cell capacitance, with current densities being greater in larger cells. 4. The effects of partial blockade of i(K,r) by 0.1 microM E-4031 on spontaneous action potentials were greater in smaller cells. 5. It is concluded that there are cell size-dependent differences in the density of the i(K,r) and i(K,s) components, and these may be involved in the heterogeneity of the electrical activity of single sinoatrial node cells as well as that of the intact sinoatrial node.

Action Potentials↗
PubMed2001

Estrogen protects neuronal cells from amyloid beta-induced apoptotic cell death.

Accumulating studies have shown that estrogen replacement therapy reduces the risk of Alzheimer's disease. In this study, we clarified that 17beta-estradiol (E2) significantly rescues PC12 neuronal cells from amyloid beta protein (Abeta)-induced cell death. We found that the amino acid residues of 25 to 35 (Abeta25-35) were more cytotoxic than the full length protein (Abeta1-40) and these residues induced DNA fragmentation typical for apopto- sis. In addition, E2 was confirmed to inhibit calcium influx and cytochrome c release induced by Abeta25-35. Since these sequential events cause apoptosis, the protective effect of E2 may be exerted not by the direct interaction with Abeta, but by the blockade of the mitochondrial apoptotic pathway induced by Abeta.

Alzheimer Disease↗
PubMed2001

Gonadal regulation of PrRP mRNA expression in the nucleus tractus solitarius and ventral and lateral reticular nuclei of the rat.

We investigated the prolactin-releasing peptide (PrRP) gene expression quantitatively in the rat brain and the involvement of estrogen and progesterone using in situ hybridization. The strongest signals were observed in the nucleus tractus solitarius (NTS), which showed approximately 70% of total PrRP mRNA in the brain. Moderate expression was observed in the ventral and lateral reticular nuclei (VLRN) of the medulla oblongata. PrRP mRNA signals in the hypothalamic ventromedial- and dorsomedial nuclei showed only 5% of total signals. The PrRP mRNA expression among female rats showing normal gonadal cycle and male rats showed that the highest levels were in female rats in proestrus. Administration of estrogen or progesterone after ovariectomy induced an increase in PrRP mRNA expression in the NTS. PrRP mRNA content in the NTS increased with the progress of the pregnancy and reached a peak on the 14th day, the mid-period of pregnancy, when plasma progesterone increases. We also observed the colocalization of PrRP and estrogen receptor alpha in the neurons distributed in the NTS by double labeling immunocytochemistry. These findings indicate that PrRP gene expression is regulated by gonadal steroid hormones in the medulla oblongata, and parts of PrRP synthesizing neurons are considered to be directly influenced by estrogen in the NTS.

Animals↗
PubMed2001

Gap junction remodeling in hypertrophied left ventricles of aortic-banded rats: prevention by angiotensin II type 1 receptor blockade.

Remodeling of gap-junctional organization in hypertrophied left ventricle (LV) in response to pressure overload in rats induced by abdominal aorta banding was investigated by immunoconfocal and electron microscopy. Eight to 12 weeks after banding, rats developed significant LV hypertrophy. In contrast to control LV myocytes, which showed connexin43 (Cx43) labeling largely confined to the intercalated disks, LV myocytes from aortic-banded rats showed dispersion of punctate Cx43 labeling over the entire cell surface. In LV tissues sectioned longitudinally, the proportion of Cx43 label at the intercalated disk decreased significantly (control, 0.87 v aortic-banded, 0.62). En-face views of intercalated disks of hypertrophied myocardium revealed a reduction of Cx43 gap junctions in the disk center, giving rise to a significant decrease in the proportion of the disk occupied by gap-junctional membrane (control, 0.32 v aortic-banded, 0.24). Electron microscopy of hypertrophied LV tissue revealed that Cx43-containing gap junctions were frequently displaced from their usual locations to form side-to-side contacts distant from the disk, and also appeared as annular profiles. In aortic-banded rats treated with the angiotensin II (AII) type 1 receptor (AT1) antagonist, losartan (10 mg/kg/day, 11 weeks) not only LV hypertrophy, but also the gap junction disorganization was markedly reduced. These results suggest that LV hypertrophy induced by pressure overload is associated with Cx43 gap junction disorganization and that AII may play an important role either directly or indirectly in gap-junctional remodeling.

Angiotensin Receptor Antagonists↗
PubMed2001

Localization of interferon regulatory factor-1 in human endometrium throughout the menstrual cycle.

OBJECTIVE: To determine the expression and localization of IRF-1 in human endometrium throughout the menstrual cycle. DESIGN: A comparative study. SETTING: Department of Obstetrics and Gynecology, Kyoto Prefectural University of Medicine. PATIENTS: Thirty-eight women aged 33 to 46 years, with regular menstrual cycles and nonpathological endometrium, undergoing hysterectomy. INTERVENTION(S): Endometrial tissues were obtained from operative samples. MAIN OUTCOME MEASURE(S): Expression of IRF-1 mRNA throughout the menstrual cycle was investigated using semiquantitative reverse transcription-polymerase chain reaction. Localization of IRF-1 protein was determined using immunohistochemistry. RESULT(S): IRF-1 mRNA was expressed in the human endometrium at each phase of the menstrual cycle. The immunoreactivity for IRF-1 was observed in the extranuclear compartment of the surface and glandular epithelial cells, both during the proliferative and secretory phases, as well as in the gland secretion during the secretory phase. In contrast, stromal cells were nearly unstained. CONCLUSION(S): IRF-1 was localized in the human endometrium, implying that this nuclear protein plays some role other than as a transcription factor.

Adult↗
PubMed2001

Immunohistochemical localization of aromatase and apoptosis-associated proteins in ovarian serous cystadenocarcinoma arising from ovarian endometriosis.

An immunohistochemical study was made of a case of serous cystadenocarcinoma that had been shown to have arisen from ovarian endometriosis. Aromatase cytochrome P450 (P450arom), an enzyme responsible for estrogen biosynthesis, was localized in the epithelial linings of the endometriosis and faintly in the transitional part, whereas it was not expressed in the carcinoma tissue. In contrast, estrogen receptors, progesterone receptors, and apoptosis-associated proteins, Fas, Fas ligand, and Bax were expressed in both endometriosis and carcinoma tissues of the tumor, whereas Bcl-2 was not expressed in either tissue of the tumor. It was suggested that the undifferentiated shift of the histologic grade might result in the loss of P450arom and that the malignant transformation was not caused by an altered balance of apoptosis-associated proteins. Accumulation of these studies may lead to a better understanding of the nature of malignant transformation of ovarian endometriosis.

Adult↗
PubMed2001

Oestrogen receptor-alpha gene polymorphism is associated with endometriosis, adenomyosis and leiomyomata.

Endometriosis, adenomyosis and leiomyomata develop in women of reproductive age and regress after menopause or ovariectomy, suggesting that they grow in an oestrogen-dependent fashion. We investigated whether polymorphism in the oestrogen receptor-alpha (ERalpha) gene is related to oestrogen-dependent benign uterine disease. A total of 203 women with regular menstrual cycles underwent laparotomy or laparoscopy and were diagnosed histologically with endometriosis, adenomyosis and/or leiomyomata. Patients with cervical carcinoma in situ, tubal occlusion or adhesion but no other gynaecological disease were considered to be disease-free. A total of 179 women undergoing annual health examination were grouped as reference population. The distribution of PVUII genotypes (PP, Pp, and pp) of the ERalpha gene was different between each pair of the four groups of endometriosis, adenomyosis/leiomyomata, disease-free, and reference population (P = 0.022-0.0005), except between the former two groups. The PP genotype was less frequent in the groups of endometriosis (P = 0.0002) and adenomyosis/leiomyomata (P = 0.002) as compared to that in the disease-free group. In the endometriosis group, there was no difference in the distribution of PVUII genotypes due to complicating diseases (adenomyosis and/or leiomyomata) or severity of the clinical stages. These results suggest that the PVUII polymorphism of the ERalpha gene is associated with the risk for endometriosis, adenomyosis, and leiomyomata.

Adult↗
PubMed2001

Progesterone inhibition of functional leptin receptor mRNA expression in human endometrium.

Leptin is secreted by adipocytes and regulates appetite through interaction with hypothalamic leptin receptors (OB-R). Leptin is involved in the stimulation of reproductive functions, and local expression of leptin and OB-R in the ovary, oocyte, embryo, and placenta might play a role in early development. The mRNA and protein of the long form leptin receptor (OB-R(L)) but not of leptin are expressed in the human endometrium and the abundance of OB-R mRNA expression varies during the menstrual cycle with a peak in the early secretory phase. We examined the steroidal regulation of OB-R(L) mRNA expression. Northern blot analyses showed that in organ-cultured proliferative endometrial specimens, oestradiol (10(-9) and 10(-8) mol/l) had no acute effect on the OB-R(L) mRNA expression, whereas oestradiol plus progesterone (10(-8), 10(-7) and 10(-6) mol/l) or medroxyprogesterone acetate (10(-8) and 10(-7) mol/l) suppressed the expression by approximately 50%. This progestin-induced suppression was blocked by a concomitant addition of mifepristone. Additionally, incubation of endometrial specimens in the presence of leptin resulted in the phosphorylation of its intracellular target, STAT3 (signal transducer and activator of transcription 3). These results indicate that, in the human endometrium, progestins act via the progesterone receptors to suppress functional OB-R(L) mRNA expression, and may thereby alter the sensitivity of the endometrium to leptin.

Adult↗
PubMed2001

A novel detection method for 2'-deoxyoxanosine.

2'-Deoxyoxanosine (dOxo) is a novel DNA lesion produced from 2'-deoxyguanosine by the treatment with nitrous acid and nitric oxide. However, there has been no direct evidence on the formation of dOxo in vivo so far. In order to detect dOxo in vivo, we have explored a sensitive detection method specific for dOxo by using a fluorescent labeling reagent and HPLC analysis. An efficient method to detect the dOxo formation in DNA is described.

Chromatography, High Pressure Liquid↗
PubMed2001

Pacemaker shift in the rabbit sinoatrial node in response to vagal nerve stimulation.

Effects of brief postganglionic vagal nerve stimulation on the activation sequence of the rabbit sinoatrial (SA) node were investigated. Activation sequences in a small area (7 mm x 7 mm) on the epicardial surface were measured in a beat-to-beat manner using an extracellular potential mapping system composed of 64 modified bipolar electrodes with high-gain and low-frequency band-pass filtering. The leading pacemaker site was recognised clearly from both the activation sequence and the characteristic morphology of the potentials. Vagal stimulation resulted in a short-lasting initial slowing of spontaneous rate followed by a long-lasting secondary slowing; a brief period of relative or absolute acceleration was interposed between the two slowing phases. During these changes of spontaneous rate, the leading pacemaker site shifted in a complex beat-to-beat manner by 1-6 mm alongside the crista terminalis in the superior or inferior direction. For the first spontaneous excitation following stimulation, the greater the slowing, the larger the distance of the pacemaker shift. There was no such linear relationship between the extent of slowing and the distance of pacemaker shift for the subsequent beats. These changes in the leading pacemaker site in response to vagal stimulation may be the result of the functional and morphological heterogeneity of the mammalian SA node in terms of innervation, receptor distribution and ion channel densities. Experimental Physiology (2001) 86.2, 177-184.

Animals↗
PubMed2001

Possible involvement of Rho kinase in Ca2+ sensitization and mobilization by MCh in tracheal smooth muscle.

We examined the effects of Rho kinase on contraction and intracellular Ca2+ concentration ([Ca2+](i)) in guinea pig trachealis by measuring isometric force and the fura 2 signal [340- to 380-nm fluorescence ratio (F340/F380)]. A Rho kinase inhibitor, Y-27632 (1-1,000 microM), inhibited methacholine (MCh)-induced contraction, with a reduction in F340/F380 in a concentration-dependent manner. The values of EC(50) for contraction and F340/F380 induced by 1 microM MCh with Y-27632 were 27.3 +/- 5.1 and 524.1 +/- 31.0 microM, respectively. With 0.1 microM MCh, the values for these parameters were decreased to 1.0 +/- 0.1 and 98.2 +/- 6.2 microM, respectively. Tension-F340/F380 curves for MCh indicated that Y-27632 caused an ~50% inhibition of MCh-induced contraction, without a reduction in F340/F380. These effects of Y-27632 were not inhibited by a protein kinase C inhibitor, GF-109203X. Our results indicate that inhibition of Rho kinase attenuates both Ca2+ sensitization and [Ca2+](i).

Amides↗