Biomedical subjects

Y Imai

Publications and source records attributed to Y Imai.

At least 379 records · Page 21Linked to original sources

PubMed1997

Effects of GTP on bound nitric oxide of soluble guanylate cyclase probed by resonance Raman spectroscopy.

Soluble guanylate cyclase (sGC) was isolated from bovine lung, and its resonance Raman (RR) spectra were investigated for the reduced, CO-bound (CO-sGC), NO-bound (NO-sGC), oxidized, and oxidized NO-bound forms in the presence and absence of GTP. The enzyme was purified by more than 12 000-fold in terms of specific activity than the supernatant of homogenates, and the heme content was determined with the pyridine hemochoromogen method and Bradford's protein assay to be 0.8 per heterodimer (alpha, Mr = 74 000; beta, Mr = 69 000). The RR spectra of sGC and CO-sGC including the Fe-His stretch at 203 cm-1 and the Fe-CO stretch at 473 cm-1 were unaltered by binding of GTP and cGMP, but apparent RR spectra of NO-sGC in the presence of GTP changed with time and concentrations of GTP. In the absence of GTP, the RR bands of the N-O stretch (nuNO) and the Fe-NO stretch (nuFe-NO) were observed at 1681 and 521 cm-1, respectively. In its presence, however, two nuNO bands were observed at 1700 and 1681 cm-1, which exhibited 15NO isotopic frequency shifts of 32 and 34 cm-1, respectively. Similar Raman spectral changes were observed with the same amount of cGMP but not with PPi or GTP analogues including ATP, GMPPNP, and GTPgammaS. This suggests that GTP or cGMP binds to the distal side of the heme in the proximity of bound NO, possibly regulating NO binding.

Animals↗

PubMed1997

rGbeta1: a psychostimulant-regulated gene essential for establishing cocaine sensitization.

Repeated doses of cocaine or amphetamine lead to long-lasting behavioral manifestations that include enhanced responses termed sensitization. Although biochemical mechanisms that underlie these manifestations currently remain largely unknown, new protein synthesis has been implicated in several of these neuroadaptive processes. To seek candidate biochemical mechanisms for these drug-induced neuroplastic behavioral responses, we have used an approach termed subtracted differential display (SDD) to identify genes whose expression is regulated by these psychostimulants. rGbeta1 is one of the SDD products that encodes a rat G-protein beta subunit. rGbeta1 expression is upregulated by cocaine or amphetamine treatments in neurons of the nucleus accumbens shell region, a major center for psychostimulant effects in locomotor control and behavioral reward. Antisense oligonucleotide treatments that attenuate rGbeta1 expression in regions including the nucleus accumbens abolish the development of behavioral sensitization when they are administrated during the repeated cocaine exposures that establish sensitization. These treatments fail to alter acute behavioral responses to cocaine, and they do not block the expression of cocaine sensitization when it is established before oligonucleotide administrations. Full, regulated rGbeta1 expression is a biochemical component essential to the establishment of a key consequence of repeated cocaine administrations, sensitization.

Amino Acid Sequence↗

PubMed1997

Molecular cloning of a novel polypeptide, DP5, induced during programmed neuronal death.

To study the molecular mechanisms underlying neuronal programmed cell death (PCD), we performed differential display screening for genes, the expression of which was induced during PCD in the sympathetic neuron culture model deprived of NGF. We cloned a gene encoding a novel polypeptide (DP5) which consisted of 92 amino acids. DP5 polypeptide had no homology with any other known protein and contained no motif that would indicate its putative biochemical functions. DP5 mRNA levels peaked at 15 h after nerve growth factor withdrawal, concurrent with the time at which neurons were committed to die. The induction of DP5 gene expression was blocked when cell death was rescued by treatment with cycloheximide, KCl, or the cyclic AMP analogue CPTcAMP. Overexpression of the full-length DP5 in cultured sympathetic neurons was in itself sufficient to induce apoptosis. These results suggest that DP5 plays a role in programmed neuronal death.

Amino Acid Sequence↗

PubMed1997

Effects of endocrine therapy on the primary lesion in patients with prostate carcinoma as evaluated by endorectal magnetic resonance imaging.

BACKGROUND: Little effort has been made at the quantitative and qualitative evaluation of patients with prostate carcinoma, including downsizing and downstaging of the primary lesion, after conservative therapy. The current study was undertaken to investigate the qualitative and quantitative effects of endocrine therapy on the primary prostate carcinoma using magnetic resonance imaging (MRI). METHODS: The primary prostate carcinoma was evaluated by endorectal MRI approximately 4 months after the initiation of endocrine therapy in 48 patients with histologically confirmed prostate carcinoma detected by endorectal MRI before therapy. RESULTS: The volumes of the prostate gland, the carcinoma, and the noncarcinomatous components were reduced to 60.2 +/- 2.7%, 25.5 +/- 2.9%, and 83.2 +/- 6.3% of their pretreatment volumes respectively after endocrine therapy, indicating that the tumors are more susceptible to endocrine therapy than the nontumorous components. The number of prostate carcinomas that demonstrated low signal intensity compared with the normal peripheral zone on T2-weighted images decreased after endocrine therapy and the number of carcinomas with enhancement of T1-weighted contrast-enhanced images increased after therapy. Seven of the 48 patients underwent downstaging after endocrine therapy, based on the endorectal MRI evaluation. CONCLUSIONS: The results of the current study suggest that downsizing and occasionally downstaging of the carcinoma may occur after endocrine therapy in patients with prostate carcinoma. In addition, the androgen sensitivity of the prostate carcinoma tissue is relatively high compared with the residual noncancerous prostate gland.

Antineoplastic Agents, Hormonal↗

PubMed1997

Affinity labeling displays the stepwise activation of ICE-related proteases by Fas, staurosporine, and CrmA-sensitive caspase-8.

The activation of multiple interleukin-1beta converting enzyme-related proteases (caspases) in apoptotic mammalian cells raises questions as to whether the multiple active caspases have distinct roles in apoptotic execution as well as how these proteases are organized in apoptotic signaling pathways. Here we used an affinity-labeling agent, YV(bio)KD-aomk, to investigate the caspases activated during apoptotic cell death. YV(bio)KD-aomk identified six distinct polypeptides corresponding to active caspases in Fas-stimulated Jurkat T cells. On staurosporine treatment, four polypeptides were detected. Competition experiments showed that the labeled caspases have distinct substrate preferences. Stepwise appearance of the labeled caspases in each cell death event was consistent with the view that the activated caspases are organized into protease cascades. Moreover, we found that stepwise activation of caspases similar to that induced by Fas ligation is triggered by exposing non-apoptotic Jurkat cell extracts to caspase-8 (MACH/FLICE/Mch5). Conversely, CrmA protein, a viral suppressor of Fas-induced apoptosis, inhibited the protease activity of caspase-8. Overall, these findings provide evidence that caspase-8, a CrmA-sensitive protease, is responsible for initiating the stepwise activation of multiple caspases in Fas-stimulated cells.

Affinity Labels↗

PubMed1997

HLA class I-restricted and tumor-specific cytotoxic T lymphocytes from metastatic lymph nodes of esophageal cancers.

This paper investigates the presence of HLA class I-restricted and tumor-specific cytotoxic T lymphocytes (CTL) in tumor sites of esophageal cancers. Five CTL lines were established from the metastatic lymph nodes or pleural effusion by incubation with interleukin-2 of tumor-infiltrating lymphocytes: cases 1 and 5, HLA-A26- and HLA-A33-restricted and squamous cell carcinoma (SCC)-specific CTL; case 2, HLA-Cw0102-restricted and esophageal SCC-specific CTL; case 3, HLA-A24- and HLA-A26-restricted CTL recognizing histologically different tumor cells; and case 4, HLA-A26-restricted and esophageal SCC-specific CTL. These results suggest the existence of HLA class I-restricted and tumor-specific CTL in metastatic esophageal SCC.

Aged↗

PubMed1997

The crystal structure of human cathepsin L complexed with E-64.

We have determined the three dimensional structure of the complex of human cathepsin L and E-64, an irreversible inhibitor of cysteine proteases, at 2.5 A resolution. The overall structure was similar to that of other known cysteine proteases and apparently identical to the mature region of procathepsin L. The electron density for E-64 is clearly visible except for the guanidinobutane moiety. From comparison of the active sites of cathepsin L and B, we found the following: (1) The S' subsites of cathepsin L and B are totally different because of the 'occluding loop' lying on the end of the S' subsites of cathepsin B. (2) The S2 pocket of cathepsin L is shallow and narrow compared to that of cathepsin B. (3) The S3 subsites of the two enzymes are more similar than the other subsites, but cathepsin L may accommodate a more bulky group at this site. Knowledge of the active site structure of cathepsin L should be helpful for the structure-based design of potent and specific inhibitors which are of therapeutic importance.

Cathepsin L↗

PubMed1997

Mutations of the Ki-ras, p53 and APC genes in adenocarcinomas of the human small intestine.

In contrast to the origins of colorectal carcinomas, the mechanisms of carcinogenesis in the small intestine remain unclear. We therefore analyzed the mutational status of the Ki-ras, p53, and adenomatous polyposis coli (APC) genes in primary carcinomas of the small intestine and compared the mutation patterns with those established for colorectal cancers. DNA was extracted from 15 formalin-fixed, paraffin-embedded lesions. Codons 12, 13 and 61 of the Ki-ras gene, exons 5-8 of the p53 gene, and codons 1268-1569, which contain the mutation cluster region (MCR) of the APC gene, were amplified by means of PCR, subcloned and sequenced. Mutations of the Ki-ras and p53 genes were observed in 8 (53.3%) and 4 lesions (26.7%), respectively. The mutational frequency of the Ki-ras gene in the present series of small intestinal carcinomas was similar, while that of the p53 gene was slightly lower than the reported frequencies for colorectal carcinomas. Only one case showed a mutation of the APC gene, involving an insertional mutation of an adenine at codons 1554-1556 with formation of a stop codon immediately downstream. Since the occurrence of an APC mutation is considered an early event in colorectal carcinogenesis, our findings indicating an extremely low frequency of such changes in and around the MCR suggest that carcinomas of the small intestine arise via a genetic pathway distinct from that involved in the development of carcinomas of the colorectum.

Adult↗

PubMed1997

Fungal P450nor: expression in Escherichia coli and site-directed mutageneses at the putative distal region.

P450nor, nitric oxide reductase from Fusarium oxysporum, was expressed in the soluble fraction of Escherichia coli cells by modifying the N-terminal codons and utilizing the pCW vector. The modified P450nor purified to electrophoretic homogeneity had spectral and enzymatic properties identical to those of native P450nor obtained from the fungi. Residues 239 to 247 of the modified P450nor were replaced with Lys by site-directed mutagenesis. Thr-243 to His- and Arg-mutants were also created. Among 11 mutants, only the Thr-243 to Lys-mutant exhibited an absorption spectrum characteristic of a nitrogenous ligand-bound form of P450 at pH 8.0 in the ferric state, but the spectrum was altered to that of the wild-type P450nor as the pH was lowered. Other mutants had spectra typical of the low- and high-spin mixed form of P450 in the ferric state. In the ferrous state, all mutants showed the same spectrum as the wild-type P450nor. Nitric oxide reductase activity was considerably decreased by the replacement of Thr-243 with Lys, His, or Arg or Ala-239 with Lys. These findings indicate that Thr-243 is located more closely to the heme iron than other residues in the putative distal helix of P450nor and plays an important role in the catalytic activity, but a specific difference in the structure of the heme pocket from other P450s is suggested.

Amino Acid Sequence↗

PubMed1997

Absorption spectral studies on heme ligand interactions of P-450nor.

Heme-external ligand interactions of P-450nor were examined spectrophotometrically and compared with those of other P-450s. Most nitrogenous ligands induced type II spectral changes on binding to ferric P-450nor, as did other P-450s. In contrast with other P-450s, 2-methylpyridine and 1-butanol induced type I changes in the spectrum of P-450nor. No spectral interaction of ferrous P-450nor with these ligands was observed. The absorption spectra of the alkyl isocyanide complexes of ferrous P-450nor exhibited the Soret peak at 427 nm with a slight shoulder at around 455 nm at neutral pH, and this shoulder was intensified as the pH was increased, suggesting that the isocyanide complexes of P-450nor existed in two states (the 430 and 455 nm states) which were in pH-dependent equilibrium in a similar manner to microsomal P-450s. However, the equilibrium was shifted mostly to the 430 nm state in the complexes of P-450nor. The findings suggest that P-450nor, especially its ferrous form, has some distinct features from P-450cam and microsomal P-450s in the distal heme environment.

Binding, Competitive↗

PubMed1997

Meiotic nuclear reorganization: switching the position of centromeres and telomeres in the fission yeast Schizosaccharomyces pombe.

In fission yeast meiotic prophase, telomeres are clustered near the spindle pole body (SPB; a centrosome-equivalent structure in fungi) and take the leading position in chromosome movement, while centromeres are separated from the SPB. This telomere position contrasts with mitotic nuclear organization, in which centromeres remain clustered near the SPB and lead chromosome movement. Thus, nuclear reorganization switching the position of centromeres and telomeres must take place upon entering meiosis. In this report, we analyze the nuclear location of centromeres and telomeres in genetically well-characterized meiotic mutant strains. An intermediate structure for telomere-centromere switching was observed in haploid cells induced to undergo meiosis by synthetic mating pheromone; fluorescence in situ hybridization revealed that in these cells, both telomeres and centromeres were clustered near the SPB. Further analyses in a series of mutants showed that telomere-centromere switching takes place in two steps; first, association of telomeres with the SPB and, second, dissociation of centromeres from the SPB. The first step can take place in the haploid state in response to mating pheromone, but the second step does not take place in haploid cells and probably depends on conjugation-related events. In addition, a linear minichromosome was also co-localized with authentic telomeres instead of centromeres, suggesting that telomere clustering plays a role in organizing chromosomes within a meiotic prophase nucleus.

Cell Nucleus↗

PubMed1997

Tumor site-selective localization of an adoptively transferred T cell line expressing a macrophage lectin.

CTLL-2 cells were transfected with an expression vector that contained cDNA of a mouse macrophage galactose/N-acetylgalactosamine-specific calcium-type lectin (MMGL) and a stable transfectant (CTL-ML) was established. These cells and mock transfectant cells (CTL-CEP) were labeled with a long-term fluorescent cell tracer, DiI. The labeled cells were intravenously injected into mice that contained established lung metastases produced by OV2944-HM-1 ovarian tumor cells. Analyses with fluorescence microscopy of a series of frozen lung sections from the recipient mice revealed that CTL-ML preferentially accumulated in the lung metastatic nodules, whereas CTL-CEP did not. Time course studies showed that the preferential accumulation was evident 3 days after adoptive transfer. We also found that OV2944-HM-1 cells bound peanut agglutinin and Vicia villosa agglutinin B4, whose sugar specificity overlaps with the specificity of MMGL. These results suggested that MMGL molecules expressed on CTLL-2 cells contributed to their selective trafficking or retention in tumor foci possibly through recognition of tumor-associated cell surface carbohydrate antigens. These results also suggested that MMGL could be used for the selective targeting of effector cells in adoptive immunotherapy.

Adoptive Transfer↗

PubMed1997

Hard work does not result in a decrease in meal quality: the case of a Japanese farming village.

Historically, when Japanese farmers engaged in hard labor, they were likely to increase their carbohydrate intake without increasing intake of other nutrients. After Japan's economic growth started in the 1960s, however, many kinds of food became available and affordable. We investigated whether farmers today have increased the nutrients in their diet in proper proportion to energy expenditures when they are engaged in farming work by comparing the quantity and quality of meals between farmers and other villagers within a small area of a farming village. The quantity of energy and other nutrients increased with farming work, but the amounts of each nutrient per unit of energy did not decrease with the increase in energy intake. The intake of each nutrient relative to the recommended dietary allowance for energy and each nutrient did not decrease with farming work either. It was concluded that the quality of meals of farmers does not decrease with the increasing energy intake for farming work when many kinds of food are available and affordable.

Adult↗

PubMed1997

Efficacy of combination therapy of interferon-alpha with ursodeoxycholic acid in chronic hepatitis C: a randomized controlled clinical trial.

The efficacy of interferon-alpha therapy in the treatment of chronic hepatitis C is still limited. A combination therapy of interferon-alpha with ursodeoxycholic acid (UDCA) was tested for its efficacy in the treatment of chronic hepatitis C by a randomized controlled study. Eighty consecutive Japanese patients with chronic hepatitis C were randomly divided into two groups: one group was treated with interferon-alpha (group A, n = 40) and the other with a combination of interferon-alpha and UDCA (group B, n = 40). In both groups, human interferon-alpha (6 million units per day) was intramuscularly injected daily for 2 weeks and then three times a week for 22 weeks: this 24-week period was followed by 24 weeks of observation. In group B, UDCA was also administered, daily at a dose of 600 mg orally, from the beginning of the interferon therapy and administration was continued for 48 weeks. The rates for ALT normalization and clearance of hepatitis C virus (HCV) viremia at the end of the 24-week interferon therapy were similar for groups A and B (58% vs 60% and 55% vs 48%, respectively). At the end of the 24-week follow-up, the sustained normalization rates for ALT levels for the two groups were not different (35% vs 43%), while the rate of clearance was higher in group B (40%) than in group A (23%), but the difference was not significant (P = 0.14). The sustained complete response, i.e., HCV RNA negativity at the end of the follow-up, as well as the maintenance of ALT normalization during the follow-up period, was more frequent in group B (38%) than in group A (18%) although the difference was not significant (P = 0.08). The rate of HCV reactivation after interferon was discontinued was significantly lower in group B (16%) than in group A (59%) (P < 0.01). Although this combination therapy did not lead to a sufficiently sustained complete response, it could serve as adjuvant antiviral therapy when a suitable dosage and administration period are determined.

Administration, Oral↗

PubMed1997

Bone mineral measurement in Japan.

Various methods for evaluating bone mineral in appendicular, and axial bone or in the whole skeleton have recently become available. As bone mineral is one of the major determinants of bone strength, its exact measurement should be useful for the diagnosis of osteoporosis, as well as for the prediction of fracture risk and monitoring of therapeutical response. The aims of this paper are to review the fundamental performance of bone mineral measurements, the improvements in DXA systems, and the progress in site-specific bone mineral instruments for the radius and calcaneus used in Japan, and to introduce diagnostic criteria for primary osteoporosis, and report on annual rates of bone loss in Japanese females.

Absorptiometry, Photon↗

PubMed1997

Time course of endothelin-1 and nitrate anion levels after cardiopulmonary bypass in congenital heart defects.

BACKGROUND: The endothelium-derived vasoconstrictor endothelin-1 (ET-1) may be involved in pulmonary hypertension (PH), but production of the endothelium-derived vasodilator nitric oxide (NO) after cardiopulmonary bypass (CPB) in congenital heart disease is unclear. METHODS: Twenty patients (age, 4 months to 12 years) were divided into three groups: severe PH (mean pulmonary-to-systemic arterial pressure ratio > 0.5) and high pulmonary flow (n = 8), mild PH (mean pulmonary-to-systemic arterial pressure ratio < 0.35) and high pulmonary flow (n = 6), and no PH and low pulmonary flow (n = 6). The mean pulmonary-to-systemic arterial pressure ratio was calculated and blood samples were taken, and NO3-, an NO metabolite, was measured. RESULTS: Levels of ET-1 in the group with severe PH and high pulmonary flow were higher than in the other groups until 6 hours after CPB, and NO3- was not changed significantly in the group with severe PH and high pulmonary flow and or the group with mild PH and high pulmonary flow during CPB. Endothelin-1 in the group with no PH and low pulmonary flow was higher than in the group with mild PH and high pulmonary flow after CPB, and NO3- in the group with no PH and low pulmonary flow significantly decreased after CPB. A positive correlation was obtained between mean pulmonary-to-systemic arterial pressure ratio and ET-1 (r = 0.742 before CPB; r = 0.689 after CPB). CONCLUSIONS: Imbalance between increased ET-1 and constant NO after CPB in the group with severe PH and high pulmonary flow could contribute to dominant effects of ET-1, which may injure the lung. The increased ET-1 and the decreased NO after CPB in the group with no PH and low pulmonary flow may induce a mechanism of protective vasoconstriction against an acute increase in pulmonary flow.

Cardiopulmonary Bypass↗

PubMed1997

Fate of trileaflet equine pericardial extracardiac conduit used for the correction of anomalies having pulmonic ventricle-pulmonary arterial discontinuity.

BACKGROUND: External conduits used for the repair of congenital heart diseases having discontinuity between the pulmonic ventricle and the pulmonary artery still carries a high risk of reoperation. Between June 1983 and June 1992, handmade equine pericardial conduit with fabricated trileaflet valve had been the conduit of choice in our institute. The aim of this study is to clarify the temporal sequence of conduit obstruction in this material and to formulate the optimal surgical strategies for this disease entity. METHODS: One hundred forty-three patients have undergone extracardiac conduit repair using this conduit. Postoperative catheterization performed within 2 months showed pulmonary to systemic ventricular systolic pressure ratio of 0.57 +/- 0.17 with the pressure gradient between pulmonic ventricle and pulmonary artery of 21.1 +/- 17.2 mm Hg. In 63 patients among the survivors, a series of Doppler two-dimensional echocardiographic images could be clearly obtained. RESULTS: Moderate-to-severe degree of pulmonary insufficiency represented only 3.2% of all cases within 3 months, which rapidly increased to 14.3% at 1 to 3 years and 32.8% at 3 to 5 years. However, the rate of increase of pulmonary insufficiency diminished beyond 5 years with 34.9% at 5 to 7 years and 40.0% at 7 to 9 years. Estimated pressure gradient calculated by Bernoulli's equation applied in the same patient subset was 4.1 +/- 7.9 mm Hg within 3 months, which progressively increased to 7.1 +/- 11.8 mm Hg at 1 to 3 years, 21.0 +/- 24.0 mm Hg at 3 to 5 years, 40.2 +/- 25.9 mm Hg at 5 to 7 years, and 71.3 +/- 34.0 mm Hg at 7 to 9 years. Among patients with a pressure gradient across the conduit of more than 40 mm Hg at follow-up catheterization, the primary cause of the obstruction was attributed to degeneration of the valve in 7 patients, whereas sternal compression was strongly suspected as the primary cause in the other 8 patients. Intimal peel was not obvious in the excised specimens. CONCLUSIONS: Degeneration of the valve in the equine pericardial conduit became prominent at 3 to 5 years after the operation, whereas the pressure gradient across the conduit continued to progress thereafter. A thick and hardened valve from degeneration and varying degrees of external compression by the sternum were delineated at the site of stenosis.

Animals↗

PubMed1997

Ventricular hypertrophy as a risk factor in ventricular septation for double-inlet left ventricle.

BACKGROUND: Ventricular septation is an option for surgical correlation of double-inlet or common-inlet left ventricle. However, the surgical risk factors of ventricular septation remain unknown. METHODS: Twenty-three patients with double-inlet or common-inlet left ventricle underwent ventricular septation. Preoperative data were compared between the survivors (n = 18) and the nonsurvivors (n = 5) to assess surgical risk factors. RESULTS: There were two early deaths (9.5%) and three late deaths (14.3%). Nonsurvivors of ventricular septation were significantly older at the time of operation (14.0 +/- 6.0 versus 7.0 +/- 5.4 years; p < 0.05) and had greater left ventricular mass (383% +/- 100% versus 206% +/- 57% of normal predicted value; p < 0.005) and greater left ventricular mass to left ventricular end-diastolic volume ratio (1.84% +/- 1.18% versus 0.77% +/- 0.17%/% of normal predicted value; p < 0.005). Univariate logistic regression analysis also revealed age at operation (p < 0.05) and mass/end-diastolic volume ratio (p < 0.05) as significant risk factors for death after operation. Multivariate regression analysis revealed that age at operation positively influenced increased mass/end-diastolic volume ratio (p < 0.001). These findings indicated that ventricular hypertrophy was one of the risk factors for ventricular septation, which had a tendency to progress with age. CONCLUSIONS: Early operation before progression of ventricular hypertrophy is recommended in patients with double-inlet or common-inlet left ventricle who have suitable anatomy for the ventricular septation procedure.

Adolescent↗