Biomedical subjects

N Yamamoto

Publications and source records attributed to N Yamamoto.

At least 289 records · Page 16Linked to original sources

PubMed1999

An examination of potential mechanisms underlying transmyocardial laser revascularization induced increases in myocardial blood flow.

Within the past few years, transmyocardial laser revascularization (TMR) has attracted the attention of cardiologists and cardiac surgeons as a therapy for patients suffering from otherwise treatable coronary artery disease. Clinical studies have consistently shown symptomatic improvement that lasts at least 1 year in a majority of patients. The original hypothesis that prompted development of the technique was that direct myocardial perfusion from the chamber could be achieved through chronically patent channels, as is the case in reptilian hearts. Results of our early studies failed to support this hypothesis and we turned to investigations aimed at testing other possible explanations. The experiments, which are reviewed in this article, showed that TMR enhances vascular growth in ischemic myocardium.

Alligators and Crocodiles↗

PubMed1999

Changes in cortical width with bone turnover in the three different endosteal envelopes of the ilium in postmenopausal osteoporosis.

Histological indicators of bone turnover were compared in the three endosteal envelopes (cancellous, endocortical, and intracortical) of iliac bone specimens obtained from 82 osteoporotic women, to assess the correlation between bone turnover and bone volume in different remodeling sites. Although there was a significant but weak correlation between the mineral apposition rate (MAR), a histological indicator of bone formation at the basic multicellular unit (BMU) level, and the three endosteal envelopes, the bone formation rate corrected for bone surface (BFR/BS) and mineralizing surface (MS/BS), indicators of the rate of bone formation reflecting activation frequency, in the cancellous and endocortical envelopes was more closely related to the rate in the intracortical envelope. The endocortical BFR/BS and MS/BS were higher than the rate in the cancellous envelope (1.6-2.1 times and 2.0-2.4 times, respectively), indicating a higher turnover rate in the endocortical envelope. According to stepwise regression analysis of the significant determinants contributing to bone mass, several histological determinants relating to bone turnover were identified: (1) trabecular thickness (Tb.Th) was a positive determinant, whereas age and cancellous bone volume referent BFR (BFR/BV) were negatively correlated determinants of the cancellous bone volume (BV/TV) (R2 = 0.50, p < 0.001); and (2) the endocortical wall thickness (W.Th) of the given side and the cortical width (Ct.Wi) of the opposite side were positive determinants, whereas the cancellous osteoid surface (OS/BS), cancellous MAR, and endocortical eroded surface (ES/BS) of the given side were the negatively correlated determinants of the Ct.Wi of the thicker cortex (R2 = 0.62, p < 0.001). In the thinner cortex, the endocortical W.Th of the given side and Ct.Wi of the opposite side were only used as the positive determinants of the Ct.Wi of the given side (R2 = 0.55, p < 0.001). In addition: (3) a significant but weak correlation was found using the intracortical BFR/BV as a positively correlated determinant of the cortical porosity (Ct.Po) in the thicker cortex (R2 = 0.17, p < 0.01). Although these histological determinants do not fully explain the mechanisms of bone loss, an increased rate of bone turnover contributes to bone loss not only in the cancellous and intracortical envelopes, but also in the endocortical envelope, indicating increased endocortical bone resorption in osteoporosis.

Aged↗

PubMed1999

Protein nucleocytoplasmic transport and its light regulation in plants.

Light exerts a great influence on gene expression, physiology and development pattern in higher plants. Protein factors involved in these processes, such as the photoreceptor, phytochrome B, a key regulatory protein, COP1, and some bZIP transcription factors have been identified and their light-regulated movement between the cytoplasm and the nucleus has been demonstrated. These findings imply that nucleocytoplasmic transport plays a crucial role in light regulation in higher plants. This review summarizes recent investigations into plant nuclear transport systems and specific cases where nucleocytoplasmic transport is subject to light regulation.

Biological Transport↗

PubMed1999

Endothelins stimulate expression of cyclooxygenase 2 in rat cultured astrocytes.

Endothelin (ET) is one of the active endogenous substances regulating the functions of astrocytes. In the present study, we examined effects of ET on cyclooxygenase (COX) expression in cultured astrocytes. ET-3 (100 nM) caused transient increases in the expression of both COX2 mRNA and protein, but not those of COX1, in cultured astrocytes. ET-induced COX2 mRNA expression was suppressed by 5 microg/ml actinomycin D, 30 microM BAPTA/AM, inhibitors of protein kinase C (1-100 nM staurosporin and 100 microM H-7), 2 microM dexamethasone, and prolonged treatment with 100 nM phorbol 12-myristate 13-acetate. ET-3 stimulated production of prostaglandin (PG) E2 in cultured astrocytes. The effect of ET-3 on the PGE2 production was diminished by actinomycin D. Indomethacin and NS398, a selective COX2 inhibitor, comparably decreased both the basal and the ET-stimulated PGE2 production. Proliferation of cultured astrocytes was stimulated by 100 nM ET-3, and the increased proliferation was reduced by co-addition of 1 microM PGE2. Treatment with 1 microM PGE2 caused astrocytic morphological changes accompanied by disappearance of stress fibers, a prominent structure of organized cytoskeletal actin in cultured astrocytes. In the presence of 10 nM ET-3, PGE2 did not show an effect on astrocytic actin organization. The present study shows that ET is an inducer of astrocytic COX2 and suggests that ET-induced PGE2 production through COX2 may be involved in the regulation of astrocytic functions.

Animals↗

PubMed1999

Activation and degradation of the transcription factor C/EBP during long-term facilitation in Aplysia.

Long-term facilitation (LTF) of the sensory-to-motor synapses that mediate defensive reflexes in Aplysia requires induction of the transcription factor Aplysia CCAAT/enhancer binding protein (ApC/EBP) as an early response gene. We examined the time course of ApC/ EBP DNA binding during the induction of LTF: Binding activity was detected within 1 h of the sensitization treatment with serotonin, reached a maximum at 2 h, and decreased after 6 h. How are DNA binding and the turnover of ApC/EBP regulated? We find that phosphorylation of ApC/EBP by mitogen-activated protein (MAP) kinase is essential for binding. MAP kinase appears to be activated through protein kinase C. We also showed that ApC/EBP is degraded through the ubiquitin-proteasome pathway but that phosphorylation by MAP kinase renders it resistant to proteolysis. Thus, phosphorylation by MAP kinase is required for ApC/EBP to act as a transcription activator as well as to assure its stability early in the consolidation phase, when genes essential for the development of LTF begin to be expressed.

Amino Acid Sequence↗

PubMed1999

Antitumor effect of vitamin D-binding protein-derived macrophage activating factor on Ehrlich ascites tumor-bearing mice.

Cancerous cells secrete alpha-N-acetylgalactosaminidase (NaGalase) into the blood stream, resulting in deglycosylation of serum vitamin D3-binding protein (known as Gc protein), which is a precursor for macrophage activating factor (MAF). Incubation of Gc protein with immobilized beta-galactosidase and sialidase generates the most potent macrophage activating factor (designated GcMAF). Administration of GcMAF to cancer-bearing hosts can bypass the inactivated MAF precursor and act directly on macrophages for efficient activation. Therapeutic effects of GcMAF on Ehrlich ascites tumor-bearing mice were assessed by survival time and serum NaGalase activity, because serum NaGalase activity was proportional to tumor burden. A single administration of GcMAF (100 pg/mouse) to eight mice on the same day after transplantation of the tumor (5 x 10(5) cells) showed a mean survival time of 21 +/- 3 days for seven mice, with one mouse surviving more than 60 days, whereas tumor-bearing controls had a mean survival time of 13 +/- 2 days. Six of the eight mice that received two GcMAF administrations, at Day 0 and Day 4 after transplantation, survived up to 31 +/- 4 days whereas, the remaining two mice survived for more than 60 days. Further, six of the eight mice that received three GcMAF administrations with 4-day intervals showed an extended survival of at least 60 days, and serum NaGalase levels were as low as those of control mice throughout the survival period. The cure with subthreshold GcMAF-treatments (administered once or twice) of tumor-bearing mice appeared to be a consequence of sustained macrophage activation by inflammation resulting from the macrophage-mediated tumoricidal process. Therefore, a protracted macrophage activation induced by a few administrations of minute amounts of GcMAF eradicated the murine ascites tumor.

Animals↗

PubMed1999

Relationship between immunoclinical status and prevalence of viral sexually transmitted diseases among human immunodeficiency virus-1 seropositive patients in Ghana.

In view of the strong association between the acquired immunodeficiency syndrome (AIDS) and sexually transmitted diseases (STDs), we screened 182 human immunodeficiency virus (HIV)-1 infected patients over a 15-month period for serological markers to previously encountered or current STDs, most of viral etiology. The relationship between their immunological and clinical status and the prevalence of STDs was assessed and compared with that of 88 HIV-seronegative patients. Hepatitis B virus and Treponema pallidum were the most frequently occurring pathogens in both HIV-1-infected and HIV-seronegative patients. Hepatitis C virus (HCV) infection was also observed in both groups, but no HIV-seronegative patient was infected with human T-lymphotropic virus type 1 (HTLV-1). The Centers for Disease Control clinical staging of A1 through C3, representing asymptomatic to severe AIDS conditions, was observed in HIV-1 patients with or without STDs. A mean CD4 count of 288 cells per microliter (95% CI of 237-340 cells per microliter) in HIV-1 patients was significantly lower (P < 0.05) than that in HIV-seronegative individuals with 1019 cells per microliter (95% CI of 924-1115 cells per microliter), irrespective of whether subjects in either group had previous or current STDs. The mean CD4 count of patients with a single infection from HIV-1 was not significantly different (P = 0.36) from that of HIV-1 patients with multiple infections. HIV-1 infection alone appears to be responsible for the marked immunodeficiency status of seropositive patients observed in this study.

AIDS-Related Opportunistic Infections↗

PubMed1999

Epitope mapping of rat neutralizing monoclonal antibody against human immunodeficiency virus type-1 by a phage peptide library: comparison with ELISA using synthetic peptides.

We generated a rat monoclonal antibody (mAb W#10) with the ability to neutralize human immunodeficiency virus type 1IIIB (HIV-1IIIB) infection. The epitope recognized by mAb W#10 was defined as R-I-Q-R-G-P-G by enzyme-linked immunosorbent assay (ELISA) with the use of synthetic peptides. The filamentous phage clones displaying random 15-amino-acid peptides on the amino terminus of the pIII coat protein reacting with mAb W#10 were identified with affinity and immunological selection procedures. Thirteen out of 16 selected phage clones contained the G-X-G-R-X-F sequence in the coat protein region representing significant homology to a part of conserved G-P-G-R-A-F sequence in the V3 loop of various HIV-1 strains. In addition, the phage clones included the G-X-G sequence in the sequence detected by synthetic peptides as the recognition site. The selected phage clones were stained by mAb W#10 specifically and were able to compete with mAb binding to cells expressing viral antigens.

Amino Acid Sequence↗

PubMed1999

Frequent occurrence of hypoalphalipoproteinemia due to mutant apolipoprotein A-I gene in the population: a population-based survey.

To determine the frequency of familial hypoalphalipoproteinemia in the general population due to mutation of the apolipoprotein A-I (apo A-I) gene, we analyzed sequence variations in the apo A-I gene. The subjects were 67 children with a low high-density lipoprotein (HDL) cholesterol level (</=38 mg/dl, below the fifth percentile in the population of this study) who were screened from 1254 schoolchildren through a school survey. Four different mutations with deleterious potential, three frameshifts and one splice site mutation, were identified in four of the subjects. The plasma apo A-I levels of the four children with apo A-I gene mutations were reduced to approximately half of the normal levels and were below the first percentile of the general population distribution (80 mg/dl). Thus, the frequency of hypoalphalipoproteinemia due to a mutant apolipoprotein A-I gene was estimated at 6% (95% CI: 2.4-14. 4%) in the subjects with low HDL cholesterol levels and 0.3% (95% CI: 0.1-0.8%) in the Japanese population. This suggests that familial hypoalphalipoproteinemia due to apo A-I gene mutations is relatively common.

Adolescent↗

PubMed1999

Phosphorothioate G3T4G3 motifs inhibits the early stage of HIV-1 infection.

It is well known that G-rich phosphorothioate oligonucleotides (G-rich PS) bind to the V3 loop of HIV-1 gp120 and inhibit HIV-1 infection. In this study, we investigated the inhibitory mechanism of a new type of G-rich PS (PS-G3T4G3) on the replication cycle of HIV-1. PS-G3T4G3 inhibits both cell to cell and cell free infections. Binding and entry assays revealed that the inhibitory step of PS-G3T4G3 occurs at the early stage of HIV-1 infection. V3 loop-specific mAb test showed that PS-G3T4G3 binds to the V3 loop and prevents its interaction with chemokine receptors. These results suggest that PS-G3T4G3 may be a novel candidate for an HIV-1 inhibitor.

Base Composition↗

PubMed1999

Localization of farnesyl diphosphate synthase in chloroplasts.

The subcellular localization of plant farnesyl diphosphate synthase (FPPS) was examined. Immunocytochemical staining using anti-FPPS1 antibody followed by electron microscopy showed that FPPS1 was localized to chloroplasts of rice mesophyll cells. Subcellular fractions from wheat leaves were examined by immunoblot analysis. FPPS was detected in the chloroplast fraction in wheat, and was protected from proteolysis following trypsin treatment of chloroplasts. FPPS was also detected in the chloroplast fraction of a dicot plant, tobacco.

Alkyl and Aryl Transferases↗

PubMed1999

Clinical application of a nonpenetrating microvascular stapling device for vascularized free tissue transfer.

It is essential to develop a method that is technically easier and faster to perform microvascular anastomosis. Therefore the authors have utilized a nonpenetrating microvascular stapling device (VCS; Auto Suture, Tokyo, Japan). Eight vascularized free tissue transfers were performed using this stapling device. All of the transferred tissues were grafted successfully. The time required to perform the stapled microvascular anastomosis ranged from 8 to 18 minutes (mean, 12 minutes). Two arterial anastomoses required suture repairs because they could not be repaired with the use of this stapling device due to thickened vessel walls and intimal dissections. The microvascular stapling device proved useful for vascularized free tissue transfers, but the vessels suitable for this technique should be chosen carefully. Not only the surgeon but also the assistant must be experienced in microscopic surgery.

Adult↗

PubMed1999

Pharmacologic characterization of FR172516: a new combined calcium channel-blocking and beta-adrenoceptor-blocking agent.

The pharmacologic characterization of FR172516, a new combined calcium channel-blocking and beta-adrenoceptor-blocking agent, was studied and compared with amlodipine in receptor-binding assay and in vivo studies. In the binding assay, Ki values of FR172516 for calcium channel and beta-receptor were 29.3 nM and 44.1 nM, respectively. In the in vivo studies with pithed rats, FR172516 shifted the dose-response curves of isoproterenol in heart rate to the right, suggesting that this compound has a antiadrenoceptor effect in vivo. The hypotensive effect of FR172516, which could be mainly attributed to its calcium channel-blocking action, was compared with that of amlodipine in normotensive Wistar rats (NTRs), spontaneously hypertensive rats (SHRs), and renal hypertensive dogs (RHDs). FR172516 showed more potent hypotensive action than amlodipine when administered intravenously to NTRs, and apparent bradycardia was seen only with FR172516. In SHRs, FR172516 showed a long-lasting hypotensive action and dose-dependently decreased heart rate, whereas amlodipine scarcely affected heart rate. In RHDs, oral administration of FR172516 once daily for 5 days decreased blood pressure without reflex tachycardia or an increase of plasma renin activity. On the other hand, amlodipine, in the dose at which hypotensive effects equipotent to those of FR172516 were observed, produced apparent reflex tachycardia and concomitant increase of plasma renin. These results indicate that FR172516 has a potent long-lasting antihypertensive effect without activating sympathetic tone by calcium channel-blocking and beta-adrenoceptor-blocking actions.

Adrenergic beta-Antagonists↗

PubMed1999

A comparison of the binding characteristics of class I antiarrhythmic agents for human muscarinic m1-m3 receptors.

The binding characteristics of the class 1 antiarrhythmic agents, cibenzoline, disopyramide, disopyramide metabolite (the main active metabolite of disopyramide in humans), and pirmenol, for human muscarinic receptors (m1-m3) stably expressed in Chinese hamster ovary cells (CHO) were investigated by binding assay with [3H]N-methylscopolamine ([3H]NMS) as a ligand. All of these agents inhibited the specific [3H]NMS binding to membrane preparations in a concentration-dependent manner. The potencies of affinity of these agents for m1, m2, and m3 receptors (compared by IC50) were disopyramide > pirmenol > disopyramide metabolite > cibenzoline, pirmenol > cibenzoline > disopyramide > disopyramide metabolite, and disopyramide > disopyramide metabolite > pirmenol > cibenzoline, respectively. Some competition curves of cibenzoline, disopyramide, and pirmenol were shallow, and Hill coefficients of these curves differed from unity, suggesting that these agents have allosteric binding characteristics for human muscarinic receptors. The m2-selective ratios to m1 (IC50 m1/IC50 m2) and m3 (IC50 m3/IC50 m2) of cibenzoline were 4.0 and 16, and those of pirmenol were 6.5 and 43, respectively, whereas those of disopyramide and its metabolite ranged from 0.46 to 1.6, suggesting that cibenzoline and pirmenol exerted high selectivity to the m2 receptor. We conclude that (a) all class 1 antiarrhythmic agents in this study have inhibitory effects on human m1, m2, and m3 receptors, and some of those binding may show allosteric characterization; (b) disopyramide and its metabolite have similar affinity to m1 to m3 receptors; and (c) cibenzoline and pirmenol have high m2-selective ratios to m1 and m3.

Animals↗

PubMed1999

Preischemic and postischemic treatment with a new Na+/H+-exchange inhibitor, FR183998, shows cardioprotective effects in rats with cardiac ischemia and reperfusion.

This study describes the pharmacologic profile of a new Na+/H(+)-exchange inhibitor, FR183998, in anesthetized rats. FR183998 had a potent inhibitory effect on Na+/H+ exchange of rat lymphocytes with median inhibitory (IC50) value of 0.3 nM. Treatment with FR183998 (0.01-0.32 mg/kg, i.v.) reduced or completely abolished ventricular fibrillation and mortality induced by 5-min ischemia followed by reperfusion, when it was administered not only 5 min before ischemia but also 1 min before reperfusion. Myocardial infarct size induced by 30-min ischemia and 60-min reperfusion was reduced significantly in a dose-dependent manner by FR183998 (0.1-1.0 mg/kg, i.v.) when the drug was administered preischemically or at an early phase of ischemia. The ventricular tachycardia and the ventricular fibrillation observed during the ischemic period also were suppressed significantly. These results indicate that FR183998 has a strong inhibitory effect on Na+/H+ exchange and suggest that treatment with FR183998 either before or immediately after the onset of ischemia can prevent the occurrence of arrhythmias and myocardial cell necrosis in situations of ischemia and reperfusion.

Anesthesia↗

PubMed1999

Anti-HIV-1 activity of an ionically modified porous polypropylene membrane determined by filtration of a viral suspension.

We describe here a unique anti-HIV-1 membrane, derived from a chemically modified porous polypropylene (PP) membrane, which lowers viral infectivity upon the filtration of HIV-1 suspension. A cationic polymer, polyethyleneimine (PEI) was graft-polymerized onto the PP filter membrane (PP-PEI), and infectious HIV-1(HTLV-IIIB) derived from MOLT-4/HIV-1(HTLV-IIIB) cells (HIV-1(HTLV-IIIB(MOLT-4)) was applied. When a viral suspension of high titer (10(3.93) TCID50 ml(-1) was filtered, efficient reduction (>99%) of gag p24 antigen levels and infectious titer resulted. In a viral suspension of medium titer (10(2.37) TCID50 ml(-1), a significant decrease in the p24 antigen did not occur, although the titer was markedly reduced (>95%). Electron microscopic observation suggested that PEI induced viral aggregations under high titer conditions, and under medium titer conditions, PEI deprived HIV-1(HTLV-IIIB(MOLT-4)) of its infectivity alone to avoid virus adsorption. In contrast, HIV-1 propagated in human peripheral blood mononuclear cells (PBMC) such as HIV-1(HTLV-III(PBMC)) was more efficiently trapped by PP-PEI at lower titers as compared with HIV-1(HTLV-IIIB(MOLT-4)) from MOLT-4/HIV-1(HTLV-IIIB) cells. These data suggest host cell modification in the interactions between PP-PEI and HIV-1 strains. Since HIV-1(HTLV-IIIB(MOLT-4)) and HIV-1(HTLV-IIIB(PBMC)) were almost electrically neutral and negative, respectively, we concluded that the divergent effect of PEI on each HIV-1(HTLV-IIIB) resulted from their different electrical characteristics.

Cell Line↗

PubMed1999

Epileptic spasms preceded by partial seizures with a close temporal association.

PURPOSE: To investigate the distinctive features of patients with West syndrome who had partial seizures followed by epileptic spasms (PS-ES). METHODS: We examined 45 patients with West syndrome whose epileptic spasms were recorded with simultaneous video-electroencephalography (EEG) monitoring between 1982 and 1996. We investigated the patients who had PS-ES and compared the PS-ES patients with the 37 patients without PS-ES. RESULTS: Of the 45 patients who had epileptic spasms in clusters (ES) and hypsarrhythmia on the interictal EEG, eight (17%) had ES preceded by partial seizures (PS) with a close temporal association. Seven of these eight were female patients. The underlying disorders were tuberous sclerosis (one patient), Aicardi syndrome (one), nonketotic hyperglycinemia (one), and focal cortical dysplasia (one). The etiology was unknown in the remaining four patients, but was suspected to be of prenatal origin in three. Three types of seizure sequence were identified: PS followed several seconds later by ES (two patients), alternating PS and ES starting with PS (three), and PS gradually replaced by ES with overlapping of the two (three). PS-ES disappeared or was replaced by other types of seizures in 1-34 months. Six patients could not walk, and all patients could not speak any sentences at age 3 years. CONCLUSIONS: Compared with patients without PS-ES, those with PS-ES more often had organic brain lesions of prenatal origin, other types of seizures before the onset of ES, asymmetric hypsarrhythmia on the EEG, and poor psychomotor outcome.

Age of Onset↗

PubMed1999

Mechanical properties of collagen fascicles from the rabbit patellar tendon.

Tensile and viscoelastic properties of collagen fascicles of approximately 300 microns in diameter, which were obtained from rabbit patellar tendons, were studied using a newly designed micro-tensile tester. Their cross-sectional areas were determined with a video dimension analyzer combined with a CCD camera and a low magnification microscope. There were no statistically significant differences in tensile properties among the fascicles obtained from six medial-to-lateral locations of the patellar tendon. Tangent modulus, tensile strength, and strain at failure of the fascicles determined at about 1.5 percent/s strain rate were 216 +/- 68 MPa, 17.2 +/- 4.1 MPa, and 10.9 +/- 1.6 percent (mean +/- S.D.), respectively. These properties were much different from those of bulk patellar tendons; for example, the tensile strength and strain at failure of these fascicles were 42 percent and 179 percent of those of bulk tendons, respectively. Tangent modulus and tensile strength of collagen fascicles determined at 1 percent/s strain rate were 35 percent larger than those at 0.01 percent/s. The strain at failure was independent of strain rate. Relaxation tests showed that the reduction of stress was approximately 25 percent at 300 seconds. These stress relaxation behavior and strain rate effects of collagen fascicles differed greatly from those of bulk tendons. The differences in tensile and viscoelastic properties between fascicles and bulk tendons may be attributable to ground substances, mechanical interaction between fascicles, and the difference of crimp structure of collagen fibrils.

Analysis of Variance↗