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Biomedical subjects

H Imai

Publications and source records attributed to H Imai.

At least 37 records · Page 2Linked to original sources
PubMed2003

Apoptosis in cumulus cells during in vitro maturation of bovine cumulus-enclosed oocytes.

The aim of this study was to investigate whether apoptosis occurs in cumulus cells during in vitro maturation (IVM) of bovine cumulus-enclosed oocytes (CEOs). The bovine CEOs obtained from ovaries from an abattoir were cultured for 24 h in IVM medium in the presence or absence of 10% (v/v) fetal bovine serum. The developmental competence of enclosed oocytes, as assessed by the development of the blastocyst after IVF, was significantly higher in the serum-treated group than in the control group. The morphological features of apoptosis that were analysed by orcein staining were hardly detectable in the cumulus cells at the start (0 h) of IVM, but were evident at the end (24 h) of IVM both in the control and serum-treated groups. Genomic DNA was extracted from CEOs at 0, 6, 12, 18 and 24 h of IVM and subjected to ligation-mediated PCR (LM-PCR) to detect apoptotic internucleosomal DNA fragmentation. DNA fragmentation was hardly detectable at the start of IVM, but increased in a time-dependent manner as the IVM culture proceeded. DNA fragmentation was not observed in the oocytes, indicating that fragmentation occurs in cumulus cells. The degree of fragmentation was lower in the serum-treated group compared with the control group. The LM-PCR analysis of DNA extracted from CEOs at 24 h of IVM, in which the DNA had been pretreated with Klenow enzyme or T4 DNA polymerase, revealed that the characteristic forms of the DNA ends generated during cumulus cell apoptosis were mainly 3'-overhangs and blunt ends. In conclusion, the results of the present study demonstrate that cumulus cells in bovine CEOs spontaneously undergo apoptosis during IVM. The degree of apoptosis may be correlated with the developmental competence of the enclosed oocytes.

Animals↗
PubMed2002

Circulating corticosterone alters the rate of neuropathological and behavioral changes induced by trimethyltin in rats.

When trimethyltin (TMT) is administered to rats, the plasma corticosterone concentration rises transiently 3 to 4 days later. We examined whether plasma corticosterone plays a causative role in the TMT-induced impairment of the hippocampus as assessed by pathological and behavioral tests. TMT-administered rats were supplementally treated with either adrenalectomy or metyrapone (twice daily for the first 7 days after TMT) in order to permanently deplete or transiently suppress circulating corticosterone. Loss of pyramidal cells in the CA1 and CA3 fields, mossy fiber sprouting, and impairment of spatial memory were observed after TMT intoxication. Adrenalectomy apparently aggravated both the hippocampal damage and the spatial memory impairment induced by TMT treatment. The TMT+metyrapone treatment groups exhibited a significant reduction in pyramidal cells in both the CA1 and the CA3 regions. However, the neuronal damage in CA1 was significantly different between the TMT and the TMT+metyrapone groups. Metyrapone significantly reduced the TMT-induced damage to pyramidal cells in CA1, but not CA3, and it also abolished mossy fiber sprouting. TMT-induced learning impairment and hyperactivity were alleviated by metyrapone treatment. It is thus concluded that both the high levels of corticosterone induced by TMT and the pathologically low levels of corticosterone induced by adrenalectomy will worsen the consequences of TMT.

Adrenalectomy↗
PubMed2002

Contractile responses to reactive oxygen species in the canine basilar artery in vitro: selective inhibitory effect of MCI-186, a new hydroxyl radical scavenger.

BACKGROUND: Cerebral vasospasm is one of the important pathological phenomena which influence morbidity and mortality following subarachnoid haemorrhage. Reactive oxygen species (ROSs) generated by the autoxidation of oxyhemoglobin to methemoglobin may be one of the essential factors in the pathogenesis of cerebral vasospasm. The direct vasocontractile effects of hydrogen peroxide (H(2)O(2)), superoxide anion (O(2)(-)), and hydroxyl radical (*OH) on the canine basilar artery and the inhibitory effects of MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one), a new *OH scavenger, were investigated. METHOD: Isometric tension was recorded in basilar artery rings from dogs in vitro. H(2)O(2), pyrogallol (O(2)(-) donor), and vitamin C (VitC)/Fe(2+) (*OH-generating system) were used to generate the ROSs. FINDINGS: H(2)O(2) (10 micromol/L), pyrogallol (10 micromol/L), and VitC/Fe(2+) (100 micromol/L each) induced fast onset and transient, slow onset and transient, and sustained contraction, respectively, in the canine basilar artery. Contractions induced by H(2)O(2) were almost completely inhibited by pre-incubation with catalase (800 U/mL) and those by pyrogallol with superoxide dismutase (150 U/mL), but neither with MCI-186 (10 micromol/L). The contraction induced by VitC/Fe(2+) was clearly inhibited by pre-incubation with MCI-186, but not with catalase or superoxide dismutase. INTERPRETATION: ROSs have direct vasocontractile effects on the canine basilar artery in vitro, but different ROSs have different contractile characteristics. Such contractions might be related to the pathophysiology of cerebral vasospasm. MCI-186 had a clear and selective inhibitory effect against *OH-induced contraction in vitro. Comparison of different radical scavengers may be important in pharmacological assessment, especially targeted on cerebral vasospasm.

Animals↗
PubMed2002

Relationship between vitamin D receptor gene polymorphism and periodontitis.

UNLABELLED: Recent studies have shown that vitamin D receptor (VDR) gene polymorphism had regulatory effects on bone mineral density (BMD) and bone turnover. The VDR gene has also been indicated as a candidate gene for the susceptibility of osteoporosis. However, it is unclear whether VDR genotypes could be associated with alveolar bone loss of patients with periodontitis, or whether vitamin D receptor gene could be a candidate gene for susceptibility to periodontitis. The purpose of this study was to answer these two questions. METHODS: Twenty-four cases of adult periodontitis (AP), 37 cases of early onset periodontitis (EOP) and 39 healthy controls were recruited for the study. Individual samples of venous blood and DNA were obtained from each subject. Genotypes of the TaqI VDR gene were determined by PCR and TaqI restriction endonuclease digestion. RESULTS: One out of 24 AP patients, nine out of 37 EOP patients and two out of 39 healthy controls were detected with Tt genotype, while the rest had the TT genotype. The detected frequency of Tt genotype was significantly higher in EOP patients (24.3%) than in AP patients (4.2%) and healthy controls (5.1%). The frequency of t allele was also significantly higher in EOP patients. There was no statistical difference in the distribution of TaqI VDR genotypes between AP patients and healthy controls. The study suggests that Tt genotype might be a risk indicator for the susceptibility to EOP. Carriage of the allele (t) of the TaqI VDR gene may increase the risk of developing EOP.

Adolescent↗
PubMed2002

Specific expression of the cell cycle regulation proteins, GADD34 and PCNA, in the peri-infarct zone after focal cerebral ischaemia in the rat.

Cell cycle proteins play key roles in cell survival or death under pathological conditions. Expression of growth arrest and DNA damage-inducible protein, GADD34 and proliferating cell nuclear antigen (PCNA) have been investigated in the core and peri-infarct zone at 2 and 24 h after middle cerebral artery occlusion (MCAO). At these times after MCAO, numerous GADD34-positive cells were present, particularly in the peri-infarct zone (e.g. 24 +/- 4 and 52 +/- 6 immunopositive cells/0.25 mm2 at 2 and 24 h, respectively, in cortex). PCNA-immunopositive cells were barely detectable in the peri-infarct zone at 2 h; however, numerous PCNA-immunopositive cells were present in this zone by 24 h (0.7 +/- 0.3 and 10.6 +/- 1.5 immunopositive cells/0.25 mm2, respectively) as well as in the adjacent cortex and in the contralateral cingulate cortex. Most GADD34-immunopositive cells coexpressed the neuronal marker Neu-N with a smaller number coexpressing the microglial marker, Mrf-1. Evidence of morphologically 'abnormal' and 'normal' GADD34 immunopositive neurons was found within the peri-infarct zone. The majority of PCNA immunopositive cells were Mrf-1 positive with a smaller number Neu-N positive. Double-labelling revealed colocalization of GADD34 and PCNA in some cells within the peri-infarct zone and in the ependymal cells lining the ventricles. The presence of GADD34 and PCNA in a key anatomical location pertinent to the evolving ischaemic lesion indicates that GADD34, either alone or in combination with PCNA, has the potential to influence cell survival in ischaemically compromised tissue.

Animals↗
PubMed2002

Atrial fibrillation threshold predicted long-term efficacy of pharmacological treatment of patients without structural heart disease.

AIMS: To ascertain if an electrophysiological study could predict long-term efficacy of anti-arrhythmic drugs in the treatment of lone atrial fibrillation. METHODS AND RESULTS: Forty-four patients (36 males, 8 females, age 55.5 +/- 10.6) with paroxysmal atrial fibrillation were enrolled to undergo serial electrophysiological studies at the bedside. Two quadripolar catheters were inserted via the subclavian vein. Disopyramide (D: 2 mg/kg iv), cibenzoline (C: 1.4 mg/kg iv), aprindine (A: 2 mg/kg iv), pilsicainide (P: 2 mg/kg po) and flecainide (F: 3 mg/kg po) were tested. Atrial fibrillation threshold (AFT) was measured as the lowest current amplitude of rapid pacing (50 Hz for 1 s) to induce atrial fibrillation lasting more than 30 s. Before drug treatment, AFT was 3.9 +/- 0.3 mA. Pharmacological treatment raised AFT as follows: D 5.9 +/- 0.9 mA, C 7.6 +/- 1.2 mA, A 8.1 +/-1.1 mA, P 6.0 +/- 0.8 mA, F 7.3 +/- 1.1 mA. Recurrence of atrial fibrillation was observed during 1-year follow-up in 12% of cases when they were treated with a drug that raised AFT by 5 mA or more. On the other hand, the recurrence rate was 87% when patients were treated with a drug that raised AFT by less than 5 mA (P = 0.001). CONCLUSION: AFT was a good predictor of long-term efficacy of pharmacological treatment against atrial fibrillation.

Aged↗
PubMed2002

Alleviation of the two-cell block of ICR mouse embryos by polyaminocarboxylate metal chelators.

The present study was undertaken to examine the effects of various transition metal ion chelators, both polyaminocarboxylates (including nitrilotriacetate (NTA), ethylenediaminediacetate (EDDA), ethyleneglycolbistetraacetate (EGTA), ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentaacetate (DTPA)) and non-polyaminocarboxylates (dipicolinic acid and deferoxamine), on the development in vitro of one-cell ICR strain mouse embryos to the four-cell and blastocyst stages. The order of stability constants of polyaminocarboxylates for transition metal ions such as zinc, copper and iron is as follows: NTA < or = EDDA < EGTA < EDTA < DTPA. Addition of 10 or 100 micromol polyaminocarboxylates x l(-1) to the medium significantly enhanced the development of most one-cell embryos (66-88%) beyond the two-cell stage compared with that (< 25%) in medium without polyaminocarboxylates. Although EDDA, EDTA and DTPA at 10 micromol x l(-1) induced the development of most one-cell embryos to the four-cell stage and beyond, a higher concentration (100 micromol x l(-1)) of NTA and EGTA was required to obtain a similar result. Therefore, the ability of polyaminocarboxylates to overcome the two-cell block is not correlated with their potency to chelate transition metal ions. In contrast, the non-polyaminocarboxylates dipicolinic acid and deferoxamine, at 10 and 100 micromol x l(-1), did not have the same effect. Taken together, the results indicate that the ability of polyaminocarboxylates to overcome the two-cell block in embryo development is due to some common feature or features other than the ability to chelate transition metal ions.

Animals↗
PubMed2002

Effects of EDTA saturated with Ca2+ (Ca-EDTA) on pig, bovine and mouse oocytes at the germinal vesicle stage during maturation culture and the involvement of chelation of Zn2+ in pronuclear formation induction by Ca-EDTA.

EDTA saturated with Ca(2+), Fe(3+) or Cu(2+) can induce parthenogenetic activation of pig oocytes at the germinal vesicle stage, whereas EDTA saturated with Zn(2+), which is unable to chelate Zn(2+), does not, indicating that chelation of Zn(2+) with EDTA saturated with Ca(2+) (Ca-EDTA) in maturing pig oocytes plays a pivotal role in the induction of parthenogenetic activation of oocytes. In the present study, the involvement of Zn(2+) chelation in the induction of parthenogenetic activation of pig oocytes at the germinal vesicle stage was confirmed first by examining the effects of concomitant addition of Zn(2+), Cu(2+) or Ni(2+) at various concentrations together with 1 mmol Ca-EDTA l(-1) to the maturation medium. The titration experiments revealed that the pronuclear formation induced by 1 mmol Ca-EDTA l(-1) was completely inhibited by the addition of > 30 micromol Zn(2+) l(-1) to the medium, but not by the addition of Cu(2+) and Ni(2+) at any concentration examined. Second, bovine and mouse oocytes at the germinal vesicle stage were cultured in medium with or without 1 mmol Ca-EDTA l(-1) for 48 h to examine the effects of Ca-EDTA treatment on these oocytes during maturation culture. Most (70-86%) of the bovine oocytes that underwent germinal vesicle breakdown matured to the MII stage via the MI phase, regardless of whether Ca-EDTA was present for the first 24 h of culture. However, 61% of oocytes that had been cultured with Ca-EDTA for 48 h formed a pronucleus without a second polar body, whereas oocytes cultured in the absence of Ca-EDTA were not observed to form a pronucleus at any time during culture. However, even when mouse oocytes at the germinal vesicle stage were cultured for up to 48 h in maturation medium containing Ca-EDTA, pronuclear formation was not observed. Finally, when bovine oocytes that had been cultured with 1 mmol Ca-EDTA l(-1) for 48 h from the germinal vesicle stage were cultured further in medium without Ca-EDTA that was supplemented with 5% fetal calf serum, only 26% of the oocytes developed to the cleaved stage, and none could develop further.

Animals↗
PubMed2001

Changes in the GABA-ergic system induced by trimethyltin application in the rat.

Ingestion of trimethyltin (TMT) produces mental confusion and temporal lobe seizures in humans. In rats, it causes increased seizure susceptibility, hyperactivity, aggression, learning impairment, and neuronal loss especially of hippocampal CA3c pyramidal cells and in the piriform cortex. As some of these symptoms may be due to impaired inhibitory neurotransmission, mRNA levels of the nine major GABA(A) receptor subunits, of GABA(B) receptors 1 and 2, and the 65- and 67-kD glutamate decarboxylase (GAD) variants were investigated by in situ hybridization 2, 5, and 16 days after TMT administration. GAD-65 mRNA levels were enhanced in hippocampal interneurons by up to 46% 5 days after TMT application, suggesting increased activity of respective neurons. In the granule cell layer, only the GABA(A) receptor subunit delta mRNA was altered (decreased by 48%). In the hippocampal sector CA3c and in the piriform cortex, mRNA levels of GABA(A) receptor subunits alpha1, alpha5, beta1, beta2, beta3, gamma2 and of both GABA(B) receptors declined (by 46-72%) after 5-16 days, being consistent with the extensive cell loss. In contrast, subunit alpha2 mRNA levels decreased already after 2 days at an extent exceeding the cell loss in CA3. Subunit alpha4 mRNA levels increased (about two-fold) in surviving CA3 neurons. In sector CA1, mRNA levels of subunits alpha1, alpha5, beta2, beta3, and gamma2 decreased by 35-54% in spite of only a minor (9%) cell loss. The data indicate neurodegeneration related decreases in mRNA levels in sector CA3 and piriform cortex, whereas decreases in sector CA1 may be a consequence of impaired excitatory input to this area.

Aggression↗
PubMed2001

[Effects of smoking on pulmonary function: a cross-sectional and longitudinal study].

Cross-sectional and longitudinal studies were done to investigate the influence that a change in smoking habit can have on the pulmonary function. Seventeen hundred and thirty nine people (698 men, 1,041 women), 39 years of age or older, from the population of a farming village located in the central part of Miyazaki Prefecture were examined. A population-based cohort study with a 4-time observation was done over an interval of 12 years. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1.0) were used as the index of respiratory function, and adjusted annual change of FVC and adjusted annual change of FEV1.0 were used as a pulmonary function inspection index. There was a statistical significance in both %FVC and %FEV1.0 to the predicted values between smokers and non-smokers at the beginning of observation. The adjusted annual change of FVC both of male- and female-smokers and the adjusted annual change of FEV1.0 of male-smokers was higher than those of non-smokers in the longitudinal study. Percent FVC, %FEV1.0 and the adjusted FEV1.0 change of former male-smokers were lower than those of continuing smokers. In addition to %FVC and %FEV1.0, annual change of FVC and annual change of FEV1.0 were important predictors of pulmonary function related to cigarette smoking.

Adult↗
PubMed2001

ATRA-regulated Asb-2 gene induced in differentiation of HL-60 leukemia cells.

Suppressors of cytokine signaling (SOCS) proteins possess common structures, a SOCS box at the C-terminus and a SH2 domain at their center. These suppressors are inducible in response to cytokines and act as negative regulators of cytokine signaling. The ASB proteins also contain the SOCS box and the ankyrin repeat sequence at the N-terminus, but do not have the SH2 domain. Although Socs genes are directly induced by several cytokines, no Asb gene inducers have been identified. In this study, we screened the specific genes expressed in the course of differentiation of HL-60 cells, and demonstrated that ASB-2, one of the ASB proteins, was rapidly induced by all-trans retinoic acid (ATRA). Typical retinoid receptors (RARs) or retinoid X receptors (RXRs) binding element (RARE/RXRE) were presented in the promoter of the Asb-2 gene. We showed that RARalpha, one of the RARs, binds to the RARE/RXRE in the Asb-2 promoter. In addition, we demonstrated by luciferase reporter assay that this element was a functional RARE/RXRE. These findings indicate that ASB-2 is directly induced by ATRA and may act as a significant regulator, underlying such physiological processes as cell differentiation.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The effect of explicit financial incentives on physician behavior.

Managed care organizations use explicit financial incentives to influence physicians' use of resources. This has contributed to concerns regarding conflicts of interest for physicians and adverse effects on the quality of patient care. In light of recent publicized legislative and legal battles about this issue, we reviewed the literature and analyzed studies that examine the effect of these explicit financial incentives on the behavior of physicians. The method used to undertake the literature review followed the approach set forth in the Cochrane Collaboration handbook. Our literature review revealed a paucity of data on the effect of explicit financial incentives. Based on this limited evidence, explicit incentives that place individual physicians at financial risk appear to be effective in reducing physician resource use. However, the empirical evidence regarding the effectiveness of bonus payments on physician resource use is mixed. Similarly, our review revealed mixed effects of the influence of explicit financial incentives on the quality of patient care. The effect of explicit financial incentives on physician behavior is complicated by a lack of understanding of the incentive structure by the managed care organization and the physician. The lack of a universally acceptable definition of quality renders it important that future researchers identify the term explicitly.

Attitude of Health Personnel↗
PubMed2001

Difference in molecular structure of rod and cone visual pigments studied by Fourier transform infrared spectroscopy.

To investigate the local structure that causes the differences in molecular properties between rod and cone visual pigments, we have measured the difference infrared spectra between chicken green and its photoproduct at 77 K and compared them with those from bovine and chicken rhodopsins. In contrast to the similarity of the vibrational bands of the chromophore, those of the protein part were notably different between chicken green and the rhodopsins. Like the rhodopsins, chicken green has an aspartic acid at position 83 (D83) but exhibited no signals due to the protonated carboxyl of D83 in the C=O stretching region, suggesting that the molecular contact between D83 and G120 through water molecule evidenced in bovine rhodopsin is absent in chicken green. A pair of positive and negative bands due to the peptide backbone (amide I) was prominent in chicken green, while the rhodopsins exhibited only small bands in this region. Furthermore, chicken green exhibited characteristic paired bands around 1480 cm(-1), which were identified as the imide bands of P189 using site-directed mutagenesis. P189, situated in the putative second extracellular loop, is conserved in all the known cone visual pigments but not in rhodopsins. Thus, some region of the second extracellular loop including P189 is situated near the chromophore and changes its environment upon formation of the batho-intermediate. The results noted above indicate that differences in the protein parts between chicken green and the rhodopsins alter the changes seen in the protein upon photoisomerization of the chromophore. Some of these changes appear to be the pathway from the chromophore to cytoplasmic surface of the pigment and thus could affect the activation process of transducin.

Amino Acid Sequence↗
PubMed2001

Effects of polyunsaturated fatty acids on atrophic gastritis in a Japanese population.

In the present study, 92 people were found to have atrophic gastritis (AG) according to depressed serum levels of pepsinogen I and pepsinogen II in a screening involving 208 Japanese people, participating in a group health check. Serum levels of n-3 polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), were higher in AG than in non-AG individuals, while those of gamma-linolenic acid (GLA) were significantly lower in AG individuals. The odds ratios for high serum DHA and GLA levels in AG subjects were 2.20 (95% C.I.: 1.10-4.39) and 0.34 (95% C.I.: 0.17-0.68), respectively. The above results suggested that GLA plays a role in reducing the incidence of AG, whereas DHA may increase a risk of AG.

8,11,14-Eicosatrienoic Acid↗
PubMed2001

Chloride effect on iodopsin studied by low-temperature visible and infrared spectroscopies.

To investigate the chloride effect on the spectral properties of iodopsin, we have prepared an anion-free iodopsin (iodopsin.free) by extensive dialysis of an iodopsin sample against a buffer containing no chloride, and visible and infrared difference spectra between iodopsin.free and its photoproduct at 77 K were recorded. The absorption maximum of iodopsin.free in L-alpha-phosphatidylcholine liposomes was 528 nm, which was almost identical with that of the nitrate-bound form of iodopsin (526 nm, iodopsin.NO(3)), but 43 nm blue-shifted from that of the chloride-bound form of iodopsin (iodopsin.Cl). The iod/batho visible difference spectrum obtained from iodopsin.free was similar in shape to that from iodopsin.NO(3), but not to that from iodopsin.Cl. FTIR spectroscopy revealed that the chromophore vibrational bands and the peptide bonds of the original state in iodopsin.free were identical with those in iodopsin.NO(3) and were also similar to those in iodopsin.Cl except for the ethylenic vibrations of the chromophore. In contrast, those of the batho state in iodopsin.free were similar to those in iodopsin.NO(3) but considerably different from those in iodopsin.Cl. These results suggested that the binding of chloride but not nitrate induces a conformational change in the protein and that the chloride binding site is situated in a position where it directly interacts with the chromophore when the chromophore is photoisomerized. FTIR spectroscopy also revealed that one of the four water bands observed in the batho/iod spectrum of iodospin.Cl is absent in the spectra of iodopsin.free and iodopsin.NO(3). Thus, in contrast to nitrate, a lyotropic anion, chloride would bind to the binding site with water molecule(s) which could form a hydrogen-bonding network with amino acid residue(s) near the chromophore, thereby resulting in the red shift of the absorption maximum of iodopsin.

Amino Acid Sequence↗
PubMed2001

Serum cystatin C may predict the prognostic stages of patients with IgA nephropathy prior to renal biopsy.

The relationship between the levels of serum cystatin C and the prognostic stages of IgA nephropathy was determined in a multicenter trial in Japan. The levels of serum cystatin C in patients with IgA nephropathy were measured using the Dade Behring N Latex Cystain C assay. In 1995, the Joint Committee of the Special Study Group on Progressive Glomerular Diseases, Ministry of Health and Welfare of Japan, and the Japanese Society of Nephropathy reported four prognostic stages. These are: good prognosis group (Group I), relatively good prognosis group (Group II), relatively poor prognosis group (Group III), and poor prognosis group (Group IV), for this disease. Three-hundred and six patients with IgA nephropathy and other glomerular diseases were examined. There were no significant changes in the levels of serum creatinine (Cr) or creatinine clearance (CCr) between Group I and Group II. The mean levels of serum cystatin C in Group II were significantly higher than those in Group I (P < 0.05). The mean levels of serum cystatin C in Group III or IV were significantly higher than those in Group I (P < 0.001, P < 0.005, respectively). These suggest that the measurement of serum cystatin C may predict the prognostic stages of patients with IgA nephropathy prior to renal biopsy.

Adult↗