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Biomedical subjects

I Nakamura

Publications and source records attributed to I Nakamura.

At least 127 records · Page 7Linked to original sources
PubMed1997

Characterization of adenosine receptors mediating spinal sensory transmission related to nociceptive information in the rat.

BACKGROUND: Adenosine analogs have been shown to produce antinociception after intrathecal administration. To determine the adenosine receptor subtype involved in spinal antinociception, the effects of selective agonists and an antagonist on the evoked potentials recorded from a neonatal rat spinal cord were studied. The measured potentials are a slow ventral root potential (slow VRP), which is the C-fiber-evoked excitatory response associated with nociceptive information; a monosynaptic reflex (MSR), which reflects a non-nociceptive transmission related to motor function; and a dorsal root potential (DRP), which reflects a gamma-aminobutyric acidA (GABA(A)) receptor-mediated presynaptic inhibition associated with analgesia. METHODS: The evoked potentials were recorded in response to electric stimulation of a lumbar dorsal root. Dose-response curves of agonists for these responses were obtained to determine their relative potency order. The antagonist dissociation constants (K(D) values) were estimated by Schild analysis. RESULTS: Adenosine agonists dose dependently inhibited the slow VRP and the MSR. However, the slow VRP was five to eight times more sensitive to them than was the MSR. The rank order of agonist potency was N6-cyclohexyladenosine (CHA) = N6-(R)-phenylisopropyladenosine (R-PIA) > 5'-N-ethylcarboxamidoadenosine (NECA) >> CGS 21680 in both responses. 8-Cyclopentyltheophylline produced dose-dependent parallel shifts to the right of NECA dose-response curves for these responses. Schild analysis gave linear plots with slopes near unity. The K(D) values of CPT for the MSR and the slow VRP were estimated to be 5.5 nM and 4.3 nM, respectively. The DRP was also depressed by adenosine agonists with potency order of CHA > NECA >> CGS 21680. 8-Cyclopentyltheophylline antagonized the inhibitory effects of CHA on the DRP. CONCLUSIONS: The results indicate that adenosine agonists inhibit spinal sensory transmission related to nociception by acting at the A1 receptors. The A1 receptor also seems to be involved in transmission related to the spinal motor system. Feedback inhibition mediated by GABA(A) receptors does not contribute to this antinociceptive action.

Adenosine↗
PubMed1997

Comparison of an improved AFP kit with the intra-amniotic PSP dye-injection method in equivocal cases of preterm premature rupture of the fetal membranes.

OBJECTIVE: We developed an improved AFP kit for detecting AFP in leaked amniotic fluid. We studied the relationship between the results of the improved AFP kit and those of the intra-amniotic PSP dye-injection test (PSP test), and compared the results of two tests with the prognosis for subsequent pregnancy outcome, in order to know the diagnostic value of the two tests for preterm PROM, especially in equivocal cases. METHODS: We compared the results of the AFP kit test with those of the PSP test in 8 equivocal cases of preterm PROM (18th to 34th weeks of gestation). RESULTS: The results of the AFP kit test coincided with those of the PSP test in all 8 equivocal cases of preterm PROM. The 4 cases that tested positive resulted in preterm deliveries; and the other 4 cases that tested negative resulted in full-term deliveries. CONCLUSION: The use of the AFP kit test is useful in assessing the prognosis for subsequent pregnancy in equivocal cases of preterm PROM. The rapid and accurate AFP kit test for diagnosing preterm PROM can be substituted for the PSP test in bedside and outpatient-clinic assessments.

Adult↗
PubMed1997

Novel renin inhibitors containing (2S,3S,5S)-2-amino-1-cyclohexyl-6-methyl-3,5-heptanediol fragment as a transition-state mimic at the P1-P1' cleavage site.

A series of renin inhibitors containing the (2S,3S,5S)-2-amino-1-cyclohexyl-6-methyl-3,5-heptanediol (2-amino-3,5-anti-diol) fragment as a novel transition-state mimic was synthesized, and their biological activities were evaluated. All of the synthesized compounds containing the 2-amino-3,5-anti-diol fragment at the P1-P1' position showed high in vitro renin-inhibitory activity with IC50 values in the 10(-8)-10(-10) M range, and most of them caused a reduction of blood pressure when administered orally to salt-depleted, conscious marmosets. The inhibitor (29) with the 4-hydroxypiperidine residue at the P4 position showed the highest activity in terms of both potency and duration of the blood pressure-lowering effect.

Administration, Oral↗
PubMed1997

Specific inhibitors of vacuolar H(+)-ATPase trigger apoptotic cell death of osteoclasts.

Osteoclasts are multinucleated bone-resorbing cells that play a critical role in bone remodeling. Specific inhibitors of vacuolar H(+)-ATPase (V-ATPase), concanamycin A and bafilomycin A1, abolish bone resorption by osteoclasts. In this study, we examined whether these V-ATPase inhibitors trigger apoptotic cell death in osteoclasts, using murine osteoclast-like multinucleated cells (OCLs) formed in vitro. Acridine orange staining revealed that the treatment of OCLs with concanamycin A resulted in chromatin condensation and alterations in nuclear morphology within a few hours. The TdT-mediated dUTP-nick-end labeling (TUNEL) reaction confirmed the apoptotic features of OCLs treated with concanamycin A. The accelerated apoptotic cell death induced by concanamycin A occurred in OCLs treated with interleukin-1 alpha or macrophage colony-stimulating factor as well, which are known to elongate the survival time of osteoclasts. In contrast, these inhibitors did not induce cell death of osteoblastic cells isolated from mouse calvaria. These results suggest that functional impairment of V-ATPase triggers apoptotic cell death in osteoclasts.

Animals↗
PubMed1997

[Species-differences in diabetes-induced alterations in vasa deferentia endothelin receptors].

PURPOSE: As there is increasing evidence that diabetes induces changes in the plasma levels of endothelins (ETs) and the properties of the ET receptors in peripheral tissues and there are reports indicating the presence of significant amounts of endothelin binding sites in the mammalian vasa deferentia, we studied possible alterations in ET receptor characteristics in the vasa deferentia of rats and rabbits. METHODS: Diabetes was induced with i.v. injections of streptozotocin (65 mg/kg) and alloxan (100 mg/kg) in rats and rabbits, respectively. We investigated the binding characteristics of endothelin (ET) receptors in the vasa deferentia of four and five month experimentally-induced diabetic rats and rabbits, respectively. The densities and pharmacological properties of ET receptors in the rat and rabbit vasa deferentia were examined by radioligand receptor binding studies using [125I]ET-1. RESULTS & CONCLUSION: Receptor binding experiments with [125I]ET-1 revealed a dramatic upregulation in the expression of a single class of specific, saturable, high affinity of [125I]ET-1 binding sites in the diabetic rats but not in the vasa deferentia of diabetic rabbits. ET-1 (non-selective), ET-3 (ETC selective), BQ 610 (ETA selective) and IRL 1620 (ETB selective) compounds inhibited [125I]ET-binding to the rats and rabbits vasa deferentia consistent with the predominance of ETA receptors in these tissues.

Animals↗
PubMed1997

[Autoradiographic localization of muscarinic receptors in diabetic rat bladder].

PURPOSE: We evaluated the alterations of density, localization and subtype specificity of muscarinic receptors in experimentally-induced diabetic rat bladder. METHODS: Five groups of rats were maintained for sixteen weeks 1) diabetic, 2) diabetic insulin-treated (insulin started 8 weeks after the onset of diabetes), 3) sucrose-fed diuretic, 4) sucrose-removed and 5) age matched controls. We used radioligand binding technique and light microscopic autoradiography to define the density and distribution of muscarinic receptors in the rat urinary bladder. RESULTS & CONCLUSION: Saturation experiments showed an increase in the density of muscarinic receptors in the bladders of diabetic and diuretic rats compared with age matched controls. Insulin treatment partially reversed the up-regulatin of muscarinic receptors in rat urinary bladder. Autoradiographic studies also indicated that muscarinic receptors were located in all layers of the bladder muscularis. The muscularis of the bladder dome contained higher densities of muscarinic receptors than that of the bladder base. Lack of [3H]QNB binding to transitional epithelium, lamina propria, and tunica adventitia suggests an absence of muscarinic receptors in these regions. Inhibition of [3H]QNB binding to the bladder sections by selective muscarinic antagonists indicated existence of the M2 and M3 receptor subtypes in the muscularis of the rat bladder.

Animals↗
PubMed1996

Myocardial adaptive changes and damage in ischemic heart disease.

Changes in two of the elements of myocardial subcellular organelles relating to cardiac energetics, ventricular myosin isozymes and mitochondrial DNA mutations, were examined using left ventricular tissue samples obtained at autopsy from patients with ischemic heart disease. Myosin isozymes were examined in tissues from nine patients with ischemic heart disease and 12 control patients with cancer but no heart disease. Extracted myosin was separated by pyrophosphate gel electrophoresis. The relative concentration of each component was determined by densitometry. Mitochondrial DNA mutations were evaluated in tissues from ten patients with myocardial infarction and 11 control patients with cancer but no heart disease. DNA was extracted and mitochondrial DNA mutations were detected by the polymerase chain reaction. Two bands were revealed by pyrophosphate gel electrophoresis. These contained VM-A, which exhibited faster electrophoretic mobility and was present in lower concentrations, and VM-B, which had a lower mobility and a higher concentration, respectively. SDS polyacrylamide gel electrophoresis showed that these two components contained the heavy chain and light chains 1 and 2 of myosin. VM-A concentrations tended to be higher in patients with ischemic heart disease than in controls. A 7.4-kb deletion was detected between the D-loop and the ATPase 6 genes of mitochondrial DNA from the myocardium of 6 out of 10 patients with myocardial infarction. The relative amounts of the two myosin isozymes could be altered by ischemic heart disease, although the functional significance of these components is unclear. The changes in the two myosin isozymes might be an adaptive change to disordered energy metabolism, but this change was small. The myocardial mitochondrial DNA deletions in patients with myocardial infarction were thought to result from ischemic damage.

DNA, Mitochondrial↗
PubMed1996

Murine NK cell allospecificity-1 is defined by inhibitory ligands.

Hemopoietic allografts of normal and neoplastic origin are subject to NK cell-mediated resistance in mice. Susceptibility to this resistance is controlled by MHC-linked genes in a recessive manner. Several distinct specificities could be postulated to explain the strain-dependent pattern of resistance. These presumptive specificities for recognition are H-2 haplotype dependent, but the correspondence is not one-to-one. For example, resistance of H-2d or H-2b/d host to H-2 b graft operationally defines specificity-1, establishing its link with haplotype H-2b. To examine the molecular basis of specificity-1, spontaneous Dd-loss mutant clones were isolated from H-2b/d and H-2d hemopoietic cell lines, i.e., 416B of (C57BL/6 x DBA/2)F1 (B6D2F1) origin and L1210 of DBA/2 origin, both of which lack specificity-1. The expression of specificity-1 in the mutant clones was examined in vivo and in vitro. The results indicate that Dd-loss clones of 416B and L1210 lines express specificity-1. These data suggest that murine NK cell allospecificity-1 is defined primarily by the absence of the Dd molecule or other class I molecules sharing the protective motifs; no H-2b-associated genes play a relevant role. This conclusion is consistent with the missing self hypothesis of NK cell reactivity, and is in agreement with the observation that lysis of B6 targets by B6D2F1 NK cells is mediated mostly by cells that express Ly-49A and/or Ly-49G2.

Animals↗
PubMed1996

Interleukin-6 and soluble interleukin-6 receptors in the synovial fluids from rheumatoid arthritis patients are responsible for osteoclast-like cell formation.

Chronic immune responses and inflammatory reactions in rheumatoid arthritis (RA) often cause severe destruction of cartilage and bone, but its mechanism is still a matter of controversy. We reported that interleukin-6 (IL-6) alone does not induce osteoclast formation, but soluble interleukin-6 receptors (sIL-6R) triggered the formation in the presence of IL-6 in cocultures of murine osteoblastic cells and bone marrow cells. In this study, we examined the involvement of sIL-6R and IL-6 in joint destruction in patients with RA. Although the frequency of patients having osteoclast-like multinucleated cells in synovium derived from the knee joint was not significantly different between RA (65%) and osteoarthritis (OA) patients (43%), the number of osteoclast-like cells found in the synovium was greater in the former than in the latter. Multinucleated cells obtained from RA synovium expressed the osteoclast-specific phenotype such as tartrate-resistant acid phosphatase, carbonic anhydrase II, vacuolar proton-ATPase and vitronectin receptors at similar levels to those from a human giant cell tumor of bone. The concentration of both IL-6 and sIL-6R was significantly higher in the synovial fluids from patients with RA than with OA. The concentration of IL-6 and sIL-6R correlated well with the roentgenologic grades of joint destruction. Dose-response curves for human IL-6 and human sIL-6R in inducing osteoclast-like cell formation in cocultures indicated that the RA synovial fluids contained sufficient IL-6 and sIL-6R to induce osteoclastogenesis. When synovial fluids from RA and OA patients were added to the cocultures, some of the RA synovial fluids containing high levels of IL-6 and sIL-6R stimulated osteoclast-like cell formation, which was strikingly inhibited by adding anti-IL-6R antibody simultaneously. These results suggest that IL-6 in the RA synovial fluids is at least in part responsible for joint destruction in the presence of sIL-6R through osteoclastogenesis.

Acid Phosphatase↗
PubMed1996

Chemical and physical properties of the extracellular matrix are required for the actin ring formation in osteoclasts.

To examine the effect of extracellular matrix on osteoclast polarization, we focused on the actin organization in osteoclasts, using murine osteoclast-like multinucleated cells (OCLs) formed in cocultures of osteoblastic cells and bone marrow cells. When OCLs were cultured on either a plastic plate, calcified dentine, or calcium phosphate thin films in the presence of fetal bovine serum (FBS), they similarly formed ringed structures of F-actin dots (actin rings). However, OCLs placed on demineralized dentine or type I collagen gel matrix (collagen gel) failed to form actin rings. In the absence of FBS, actin ring formation in OCLs was induced on plastic plates coated with vitronectin, fibronectin, or type I collagen, but not on those coated with laminin, poly-L-lysine, or bovine serum albumin. Actin ring formation appeared to depend on integrins, since the GRGDS, but not the GRGES, peptide inhibited it in a dose-dependent manner. Moreover, immunoelectron microscopic examination revealed that vacuolar proton ATPase (V-ATPase) was localized along the apical membrane in much higher densities than the basolateral membrane in OCLs placed on plastic coverslips. In OCLs placed on collagen gel, however, V-ATPase was found to be distributed throughout the cytoplasm without polarity. These results suggest that actin ring formation in osteoclasts was dependent on matrix substrates, matrix proteins and integrins, and was closely related to osteoclast function.

Actins↗
PubMed1996

Osteoclast integrin alphaVbeta3 is present in the clear zone and contributes to cellular polarization.

Osteoclasts are primary bone-resorbing cells with highly polarized cytoplasmic structures, such as ruffled borders and clear zones. In the present study, we have examined the subcellular localization and function of the alphaVbeta3 integrin in primary rat osteoclasts and mouse osteoclast-like multinucleated cells (OCLs) formed in vitro. At the ultrastructural level, the specific immunoreactivity of both alphaV and beta3 subunits is localized not only along the plasma membranes of osteoclast ruffled borders and basolateral membranes but also in clear zones. Addition of GRGDS (Gly-Arg-Gly-Asp-Ser) peptide to the culture medium during a pit formation assay reduces resorbed areas on dentine slices in a dose-dependent manner. Treatment with the GRGDS peptide also dose-dependently inhibits the formation of a ringed structure of F-actin (an "actin ring") in OCLs on dentine slices. Electron-microscopic analysis has revealed that OCLs treated with GRGDS peptide at 1 mM can adhere to dentine slices with unusually broad or poorly defined clear zones but do not form the ruffled burder structure. These results suggest that integrin alphaV and beta3 subunits localized in the ruffled border/clear zone complex of osteoclasts are essential for the functional osteoclast-to-bone matrix interaction and the structural polarization of osteoclasts.

Animals↗
PubMed1996

Pathology of the cerebellar dentate nucleus in sporadic olivopontocerebellar atrophy: a morphometric investigation.

The pathology of the cerebellar dentate nucleus was investigated by morphometric methods in three patients with sporadic olivopontocerebellar atrophy (sOPCA), and the results were compared to specimens from three subjects without neurological disease (controls). The size of dentate neurons; the number of small and large neurons (50-199 microns2 and larger than 200 microns2, respectively) at rostral, middle, and caudal levels; nerve cell density; total volume of the gray band; and total nerve cell number, were estimated with an image analyzer applied to serial 20-microns-thick sections of one celloidin-embedded cerebellar hemisphere. The number of small neurons in patients with sOPCA was significantly increased at the rostral level while the number of large neurons showed large inter-individual variations. Dentate neurons also showed various qualitative changes such as atrophy and hypertrophy. The nerve cell density in the dentate nucleus was 1.7 times higher in the patients than in the controls. However, the total volume of the gray band was reduced to one-half of that in controls. There were no differences in the total nerve cell number between the patients and controls. This reduction in size of the dentate gray matter in patients with sOPCA may result from the disappearance of afferent nerve fibers originating from Purkinje cells, inferior olivary neurons, and pontine neurons.

Aged↗