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Biomedical subjects

N Yamamoto

Publications and source records attributed to N Yamamoto.

At least 307 records · Page 17Linked to original sources

Biomechanical studies of the rabbit patellar tendon after removal of its one-fourth or a half.

Effects of the overstressing induced by the harvest of grafts from the patellar tendon on the mechanical properties and morphometry of remaining tendon were studied using a rabbit model. The width of the patellar tendon was reduced by one-fourth or one-half equally removing the medial and lateral portions; by this surgery, the cross-sectional area was decreased by 25 or 50 percent from the original area. After all the rabbits were allowed unrestricted activities in cages for 3 to 12 weeks, their patellar tendons were harvested for mechanical and histological studies. The one-fourth removal induced no significant changes in the mechanical properties, but significantly increased the cross-sectional area. In the case of one-half removal, tensile strength and tangent modulus did not change in some tendons, although the cross-sectional area increased significantly. In the other central half tendons, mechanical strength decreased markedly, while the cross-sectional area increased; hypercellular areas and breakage of collagen bundles were observed in these tendons. These results indicate that the patellar tendon has an ability of functionally adapting to overstressing by changing the cross-sectional area, while keeping the mechanical properties unchanged, if the extent of overstressing is less than 30 percent.

Animals↗

Essential role of transcription factor nuclear factor-kappaB in regulation of interleukin-8 gene expression by nitrite reductase from Pseudomonas aeruginosa in respiratory epithelial cells.

Persistent infection with Pseudomonas aeruginosa increases interleukin-8 (IL-8) levels and causes dense neutrophil infiltrations in the airways of patients with chronic airway diseases. Recently, we have reported that nitrite reductase from P. aeruginosa induces the production of IL-8 in respiratory cells, including bronchial epithelial cells. To determine the molecular mechanism(s) of nitrite reductase-induced IL-8 expression in respiratory cells, A549 epithelial cells were transfected with plasmids containing serial deletions of the 5'-flanking region of the IL-8 gene and then exposed to nitrite reductase. Nitrite reductase significantly enhanced IL-8 gene promoter-driven reporter activity. This increased IL-8 gene expression was inhibited by mutating the nuclear factor-kappaB (NF-kappaB) binding element. Nitrite reductase enhanced nuclear localization of the NF-kappaB binding complex. Furthermore, nitrite reductase induced the degradation of IkappaBalpha, the major cytoplasmic inhibitor of NF-kappaB, and the expression of IkappaBalpha mRNA. These data support the critical role of the activation of NF-kappaB in nitrite reductase-induced IL-8 gene expression in airway epithelium.

DNA-Binding Proteins↗

Determinant in human immunodeficiency virus type 1 for efficient replication under cytokine-induced CD4(+) T-helper 1 (Th1)- and Th2-type conditions.

Cytokines are potent stimuli for CD4(+)-T-cell differentiation. Among them, interleukin-12 (IL-12) and IL-4 induce naive CD4(+) T cells to become T-helper 1 (Th1) or Th2 cells, respectively. In this study we found that macrophage-tropic human immunodeficiency virus type 1 (HIV-1) strains replicated more efficiently in IL-12-induced Th1-type cultures derived from normal CD4(+) T cells than did T-cell-line-tropic (T-tropic) strains. In contrast, T-tropic strains preferentially infected IL-4-induced Th2-type cultures derived from the same donor CD4(+) T cells. Additional studies using chimeric viruses demonstrated that the V3 region of HIV-1 gp120 was the principal determinant for efficiency of replication. Cell fusion analysis showed that cells expressing envelope protein from a T-tropic strain effectively fused with IL-4-induced Th2-type culture cells. Flow cytometric analysis showed that the level of CCR5 expression was higher on IL-12-induced Th1-type culture cells, whereas CXCR4 was highly expressed on IL-4-induced Th2-type culture cells, although a low level of CXCR4 expression was observed on IL-12-induced Th1-type culture cells. These results indicate that HIV-1 isolates exhibit differences in the ability to infect CD4(+)-T-cell subsets such as Th1 or Th2 cells and that this difference may partly correlate with the expression of particular chemokine receptors on these cells. The findings suggest that immunological conditions are one of the factors responsible for inducing selection of HIV-1 strains.

Cell Fusion↗

Induction of Bcl-x(L) expression by human T-cell leukemia virus type 1 Tax through NF-kappaB in apoptosis-resistant T-cell transfectants with Tax.

Human T-cell leukemia virus type 1 (HTLV-1) Tax is thought to play a pivotal role in immortalization of T cells. We have recently shown that the expression of Tax protected the mouse T-cell line CTLL-2 against apoptosis induced by interleukin-2 (IL-2) deprivation and converted its growth from being IL-2 dependent to being IL-2 independent. In this study, we demonstrate that constitutive expression of bcl-xl but not bcl-2, bcl-xs, bak, bad, or bax was associated with apoptosis resistance after IL-2 deprivation in CTLL-2 cells that expressed Tax. Transient-transfection assays showed that bcl-x promoter was transactivated by wild-type Tax. Similar effects were observed in mutant Tax retaining transactivating ability through NF-kappaB. Deletion or substitution of a putative NF-kappaB binding site identified in the bcl-x promoter significantly decreased Tax-induced transactivation. This NF-kappaB-like element was able to form a complex with NF-kappaB family proteins in vitro. Furthermore, Tax-induced transactivation of the bcl-x promoter was also diminished by the mutant IkappaBalpha, which specifically inhibits NF-kappaB activity. Our findings suggest that constitutive expression of Bcl-x(L) induced by Tax through the NF-kappaB pathway contributes to the inhibition of apoptosis in CTLL-2 cells after IL-2 deprivation.

Animals↗

Human T-cell leukemia virus type 1 tax protein abrogates interleukin-2 dependence in a mouse T-cell line.

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia. Tax, the viral protein, is thought to be crucial in the development of the disease, since it transforms healthy T cells in vitro and induces tumors in transgenic animals. We examined the effect of Tax activity on the growth of the interleukin-2 (IL-2)-dependent T-cell line CTLL-2. Stable expression of Tax in CTLL-2 transformed cell growth from being IL-2 dependent to IL-2 independent. Tax stimulated transcription through NF-kappaB and the cyclic AMP-responsive element-like sequence in the HTLV-1 promoter. The finding of Tax mutants segregating these two pathways suggested that the NF-kappaB pathway was essential for IL-2-independent growth of CTLL-2 cells while the CRE pathway was unnecessary. However, both pathways were necessary for another transformation-related activity (colony formation in soft agar) of CTLL-2/Tax. Our results show that Tax has at least two distinct activities on T cells, and suggest that Tax plays a crucial role in IL-2-independent T-cell transformation induced by HTLV-1, in addition to its well-known IL-2-dependent cell transformation.

Animals↗

Inhibitory mechanism of the CXCR4 antagonist T22 against human immunodeficiency virus type 1 infection.

We recently reported that a cationic peptide, T22 ([Tyr(5,12), Lys(7)]-polyphemusin II), specifically inhibits human immunodeficiency virus type 1 (HIV-1) infection mediated by CXCR4 (T. Murakami et al., J. Exp. Med. 186:1389-1393, 1997). Here we demonstrate that T22 effectively inhibits replication of T-tropic HIV-1, including primary isolates, but not of non-T-tropic strains. By using a panel of chimeric viruses between T- and M-tropic HIV-1 strains, viral determinants for T22 susceptibility were mapped to the V3 loop region of gp120. T22 bound to CXCR4 and interfered with stromal-cell-derived factor-1alpha-CXCR4 interactions in a competitive manner. Blocking of anti-CXCR4 monoclonal antibodies by T22 suggested that the peptide interacts with the N terminus and two of the extracellular loops of CXCR4. Furthermore, the inhibition of cell-cell fusion in cells expressing CXCR4/CXCR2 chimeric receptors suggested that determinants for sensitivity of CXCR4 to T22 include the three extracellular loops of the coreceptor.

Amino Acid Sequence↗

Mitochondrial regulation of cell death: mitochondria are essential for procaspase 3-p21 complex formation to resist Fas-mediated cell death.

Death receptor Fas transduces cell death signaling upon stimulation by Fas ligand, and this death signaling is mediated by caspase. Recently, we reported that the cell cycle regulator p21 interacts with procaspase 3 to resist Fas-mediated cell death. In the present study, the molecular characterization and functional region of the procaspase 3-p21 complex was further investigated. We observed the p21 expression in the mitochondrial fraction of HepG2 cells and detected Fas-mediated cell death only in the presence of actinomycin D. However, mitochondrial-DNA-lacking HepG2 (MDLH) cells showed this effect even in the absence of actinomycin D. Both p21 and procaspase 3 were expressed in MDLH cells, but the procaspase 3-p21 complex formation was not observed. Interestingly, the resistance to Fas-mediated cell death in the MDLH cells without actinomycin D was recovered after microinjection of HepG2-derived mitochondria into the MDLH cells. We conclude that mitochondria are necessary for procaspase 3-p21 complex formation and propose that the mitochondrial role during cell death is not only death induction but also death suppression.

Apoptosis↗

Factors contributing to pressure overload-induced immediate early gene expression in adult rat hearts in vivo.

We determined the contributions of angiotensin II type 1 receptor (AT(1)) stimulation, adrenergic stimulation, and autonomic activation to pressure overload-induced c-fos expression in the adult rat heart in vivo. c-fos expression was increased in pressure-overloaded hearts created by aortic banding compared with sham-operated rats (458 +/- 100% vs. sham, P < 0.05). GR-138950, a selective AT(1) antagonist, did not blunt this expression (banding vs. banding + GR-138950: 458 +/- 100% vs. 500 +/- 125%, not significant). Atropine and hexamethonium partially decreased c-fos expression (banding vs. banding + atropine/hexamethonium: 700 +/- 67% vs. 400 +/- 67%, P < 0.05). Phentolamine had no significant effect on c-fos expression; however, propranolol inhibited the expression (banding vs. banding + propranolol: 492 +/- 108% vs. 154 +/- 15%, P < 0.05). The inhibition by propranolol was independent of the decreases in heart rate. Thus factors contributing to pressure overload-induced c-fos expression in adult rat hearts in vivo are different from those in neonatal myocytes in vitro undergoing stretch.

Animals↗

Different brain morphologies from different genotypes in a single teleost species, the medaka (Oryzias latipes)

In a teleost fish, the medaka (Oryzias latipes), many inbred strains have been established from various origins including wild populations. Brains from five genetically different strains, which had been bred and raised under the same conditions, were examined to determine whether there is intraspecific genetic variation. A total of 25 brains from the wild-type strains (HNI-II, HB11A and HB32C) and from the body-colour mutant strains (Hi3 and HO5) were fixed, and the external features of the brains were examined under a stereomicroscope. The differences between the HNI-II brains and the Hi3 brains were the most remarkable in the external features. In order to carry out a volumetric analysis, the brains of all strains were cut into complete serial cryostat sections. Total brain volumes and relative volumes (in % of total brain volume) of the olfactory bulb, telencephalon, optic tectum, and cerebellum were calculated in each brain using a semi-automatic image analyzer. Statistical analysis showed that significant differences in the total brain volumes and the relative volumes of these subdivisions exist not only between wild-type and mutant strains but also among wild-type strains. Thus, our results demonstrate that the strains with different genotypes possess large variation in brain morphology. This is the first report to demonstrate that there exists intraspecific genetic variation in the gross brain morphology of a wild-type vertebrate.

Animals↗

Tectal fiber connections in a non-teleost actinopterygian fish, the sturgeon Acipenser.

Tectal fiber connections were studied in members of an early branch of the actinopterygian lineage, the sturgeons Acipenser transmontanus and A. schrenkii, by means of biocytin, HRP, biotinylated dextran amine, and DiI tract tracing methods. The aim of this study is to elucidate the visual pathway via the optic tectum to the thalamus as a part of a series of studies on the visual pathways in sturgeons. After biocytin or biotinylated dextran amine injections to the optic tectum terminals are found bilaterally in the medial and lateral portions of both the dorsal thalamus and ventral thalamus. Ipsilateral projections are much more abundant. Tectal recipient areas in the thalamus overlap in part with the retinal recipient areas. After HRP or DiI injections to the dorsal or ventral thalamus, tectal neurons projecting to the thalamus were labeled in the ipsilateral or bilateral stratum periventriculare. Dendritic morphology of tectothalamic neurons suggests that they receive direct retinal input. These results suggest that visual information passes through the tectum to the thalamic areas which also receive direct retinal projections. In this regard, the visual system of Acipenser resembles that of chondrichthyans (sharks). Other fiber connections of the tectum are also described, which have not previously been studied by tracer methods in a sturgeon.

Animals↗

Visual thalamotelencephalic pathways in the sturgeon Acipenser, a non-teleost actinopterygian fish.

Terrestrial vertebrates (amphibians, reptiles, birds, and mammals) possess two visual systems, the geniculate and extrageniculate pathways to the telencephalon. In cartilaginous fishes (e.g. sharks) both retinal and tectal neurons project to neurons in the thalamus, which themselves project to a single area in the telencephalon. The condition in ray-finned fishes (Actinopterygii) is ambiguous. In many teleosts there is a well developed extrageniculate pathway but no obvious geniculate system. This study reports on the thalamotelencephalic projections of a sturgeon, a non-teleost ray-finned fish. Several tract tracing methods (e.g., HRP, WGA-HRP, biocytin, BDA, DiI) were employed in conjunction with normal techniques for identifying neural structures (e.g., Nissl, Golgi). After injections of tracer into retinal and tectal recipient areas of the thalamus, labeled terminals were observed in the ventrolateral region of the caudal telencephalon, an area referred to as the thalamic projection area. After injections of tracer into the telencephalon, populations of retrogradely filled neurons were located in both the dorsal and ventral thalamus. These data demonstrate that thalamic neurons in both retinal and tectal pathways project directly to the telencephalon. These results support the view that two visual pathways are a primitive feature of vertebrate brain organization. These results are also consistent with the hypothesis that the ancestor of Acipenser and Teleostei (Actinopteri) acquired a novel visual pathway to the telencephalon through the ventral portion of the thalamus.

Animals↗

Fiber connections of the inferior lobe in a percomorph teleost, Thamnaconus (Navodon) modestus.

Afferent and efferent fiber connections of the lobus inferior (LI) were studied in a percomorph teleost, Thamnaconus (Navodon) modestus. The LI of Thamnaconus is composed of the nucleus diffusus lobi inferioris (NDLI), the nucleus recessus lateralis pars lateralis et medialis (NRLl and NRLm), and the nucleus centralis lobi inferioris pars anterior et posterior (NCa and NCp). The NDLI receives projections from the secondary gustatory nucleus, preglomerular tertiary gustatory nucleus, corpus glomerulosum, dorsal region of the area dorsalis telencephali pars medialis (dDm), and area dorsalis telencephali pars lateralis. Different subdivisions of the dorsal telencephalon project to discrete regions of the NDLI. The NDLI projects to the corpus mamillare, NRLl, NCa, and NCp. Thus the NDLI could be regarded as an intrahypothalamic relay nucleus. The NCa receives projections from the NDLI and projects to the preglomerular tertiary gustatory nucleus, secondary gustatory nucleus, nucleus lateralis valvulae, and NRLl. The NCa appears to be primarily an extrahypothalamic projection nucleus. The NCp receives projections from the NDLI. Efferent connections of the NCp remain to be studied. The NRLl receives projections from the NDLI, and projects to the nucleus ruber (NR) of Goldstein [1905] and the preglomerular tertiary gustatory nucleus. Dense projections of the NR to the stratum opticum and stratum fibrosum et griseum superficiale of the optic tectum are demonstrated. The NRLm receives projections from the medial part of the dDm. Efferent connections of the NRLm remain unclear. The LI as a whole receives projections from the locus coeruleus and nucleus raphe superior. These results suggest that the LI receives gustatory and/or general visceral information from the secondary and tertiary gustatory nuclei, visual and somatosensory inputs from the corpus glomerulosum. Inputs from the dorsal telencephalic subdivisions could be of various modalities (e.g. visual, acousticolateral, gustatory and/or general visceral). The present study also suggests that information processed in the LI is transmitted to the optic tectum via the NR, to the corpus mamillare, to the secondary and tertiary gustatory nuclei, and to the cerebellum via the nucleus lateralis valvulae.

Animals↗

Sonic motor nucleus and its connections with octaval and lateral line nuclei of the medulla in a rockfish, Sebastiscus marmoratus.

The sonic motor nucleus and its fiber connections were examined in a rockfish, Sebastiscus marmoratus by means of tracer methods using horseradish peroxidase (HRP), biocytin, and carbocyanine dye (DiI). Sebastiscus has a swimbladder and a pair of extrinsic sonic/drumming muscles. The sonic muscle is ipsilaterally innervated by the occipital nerve which is composed of two ventral roots arising from the sonic motor nucleus. The sonic motor neurons are distributed in the most ventral part of the ventral column from the caudal medulla to the rostral spinal cord, and form a ventrally located columnar nucleus. Each neuron in this nucleus possesses a long thick dendrite and several short dendrites. The long dendrite extends dorsolaterally and branches in the lateral funiculus, whereas the short dendrites branch around their cell bodies. After biocytin injections into the sonic motor nucleus, two groups of premotor neurons were retrogradely labeled bilaterally, one in the dorsomedial portion of the descending octaval nucleus (DO) and the other in the medial zone of the reticular formation (RF) in the medulla. The DO premotor neurons were multipolar with several dendrites branching near the cell bodies, and the RF premotor neurons were bipolar. One of the two dendrites of the RF premotor neurons extends laterally into the ventral portion of the DO, and the other dendrite extends into the ventromedial area in the medulla. In the ventromedial dendritic field of the RF premotor neurons, descending fibers arising from the optic tectum (TO) and torus semicircularis (TS) traverse in the tractus tectobulbaris and terminate bilaterally. After DiI insertion into the ventromedial dendritic field, retrogradely labeled neurons were found bilaterally in the TS and TO. The majority of tectal neurons were located in the stratum griseum centrale. These neurons had two short basal dendrites branching in the cell layer and a long apical dendrite extending to the stratum fibrosum et griseum superficiale and stratum opticum. The toral neurons were bipolar and were distributed throughout the TS. Furthermore, biocytin injections into the medial nucleus of the lateral line system revealed that the nucleus projects bilaterally to the RF premotor neurons. These results show that premotor neurons for the sonic motor nucleus are located in the dorsomedial portion of the DO and the medial zone of the RF in the medulla. It is suggested that the sonic motor nucleus receives auditory input via the DO premotor neurons and input from RF premotor neurons which receive lateral line input via the medial nucleus, vestibular input through the lateral dendrite extending into the ventral portion of the DO, and information from the TO and TS via the tractus tectobulbaris.

Air Sacs↗

Percutaneous transluminal coronary angioplasty, alone or in combination with urokinase therapy, during acute myocardial infarction.

To investigate the effect of pre-treatment of a thrombus with a low dose of urokinase on establishing patency in a persistent infarct-related artery (IRA) during direct percutaneous coronary angioplasty (PTCA), the frequency of acute restenosis during direct PTCA, alone, or in combination with the intracoronary administration of urokinase, was examined in a consecutive nonrandomized series of patients with acute myocardial infarction (AMI). Two hundred and seventy-two successful PTCA patients (residual stenosis <50%) were divided into 2 groups: 88 patients received pre-treatment with intracoronary urokinase following PTCA (combination group); 184 received only direct PTCA without thrombolytic therapy (PTCA group). In the present study, after achievement of a residual stenosis of less than 50%, IRA was visualized every 15 min to assess the frequency of acute restenosis, which was defined as an acute progression of IRA with more than 75% restenosis after initially successful PTCA. In the patients with a large coronary thrombus, the frequency (times) of acute restenosis was significantly lower in the combination group than in the PTCA group (0.98+/-0.19 vs 2.92+/-0.32, p<0.0001). On the other hand, in the patients with a small coronary thrombus, the frequency of acute restenosis showed no difference in either group. The present study indicates that in patients with AMI, PTCA combined with pre-treatment of a low dose of urokinase is much more effective than PTCA alone, especially for those patients who have a large coronary thrombus.

Angioplasty, Balloon, Coronary↗

Protective effect of FR168888, a new Na+/H+ exchange inhibitor, on ischemia and reperfusion-induced arrhythmia and myocardial infarction in rats: in comparison with other cardioprotective compounds.

We have studied the effects of FR168888 (5-hydroxymethyl-3-(pyrrol-1-yl)benzoylguanidine methanesulfonate), a new Na+/H+ exchange inhibitor, on ischemia and reperfusion-induced arrhythmia and myocardial infarction in anesthetized rats and compared them with those of other cardioprotective compounds. FR168888 had a potent inhibitory effect on Na+/H+ exchange of rat lymphocytes acidified with Na+-propionate with a Ki value of 6.4 nM. Pretreatment with FR168888 (0.032-0.32 mg/kg, i.v.) reduced or completely abolished the ventricular fibrillation (VF) induced by reperfusion after 5 min of regional ischemia, while lidocaine, a class I antiarrhythmic agent, showed less effect against VF as compared with FR168888. The size of myocardial infarction induced by 60-min ischemia and 60-min reperfusion was attenuated by FR168888 dose-dependently (1.0-10 mg/kg, i.v.), and ventricular tachycardia and VF were significantly reduced during the ischemic period. In contrast, propranolol and diltiazem did not show such protective effects on myocardial infarct size. In addition, FR168888 did not change hemodynamic parameters in rats. These results indicate that FR168888 has a strong inhibitory effect on Na+/H+ exchange and that treatment with FR168888 can protect the heart from arrhythmia and myocardial cell death in ischemic and reperfused situations.

Anesthesia↗

In vitro anti-human immunodeficiency virus activity of polysaccharide from Rhizophora mucronata Poir.

A polysaccharide was extracted with 1% sodium carbonate from the bark of Rhizophora mucronata and its antiviral activities against human immunodeficiency virus (HIV) were assessed by an in vitro cell culture system. The anti-HIV activity of the alkaline extract was mainly recovered in the 25-75% ethanol-precipitated fraction. Rhizophora mucronata polysaccharide (RMP) protected MT-4 cells from the HIV-induced cytopathogenicity and blocked the expression of HIV antigens. RMP completely inhibited the viral binding to the cell and the formation of syncytium upon cocultivation of MOLT-4/HIV-1IIIB cells and MOLT-4 cells. These results suggest that RMP inhibited early steps of the virus life cycle especially virus adsorption to the cell.

Anti-HIV Agents↗

Relationship between serum biochemical values and marbling scores in Japanese Black steers.

In order to obtain available biochemical parameters related to the marbling score (MS), by which the meat was graded from 1 to 12 in Japan, serum biochemical values were examined in 13 Japanese Black steers during the fattening stages. The steers were divided into high MS (8-11) and low MS (4-5) groups and the fattening stage was also divided into 4 stages according to their feed contents; Stage I (11-13 month-old; 0-4 months after the fattening (af)), II (5-9 months af), III (10-14 months af), and IV (15-20 months af). High MS group showed significantly higher levels in glucose and urea nitrogen (at Stage I), albumin/globulin ratio (at Stage II), and magnesium (at Stage I and III), and lower level in vitamin A (at Stage III) than low MS group. These biochemical parameters, indicating conditions of steers during the fattening stages, are considered to have a possibility related to MS in fattening steers.

Animals↗

Purification and characterization of an antihypertensive peptide from a yogurt-like product fermented by Lactobacillus helveticus CPN4.

Whey peptides in a yogurt-like product fermented by Lactobacillus helveticus CPN4 were fractionated by a Sep-pak C-18 cartridge followed by two-step reverse-phase HPLC. The antihypertensive activity was measured by systolic blood pressure in spontaneously hypertensive rats after oral administration of each fraction. Five major peptides in the final fraction were further purified by reverse-phase HPLC and were measured for these antihypertensive activities in spontaneously hypertensive rats. The only peptide in the final fraction that showed strong antihypertensive activity had a sequence of Tyr-Pro, which is found in alpha s1-casein (CN), beta-CN, and kappa-CN. The synthetic peptide Tyr-Pro yielded significant antihypertensive activity from 2 to 8 h after oral administration of 1 mg of peptide/kg of body weight, and the effect was maximal at 6 h after oral administration. The antihypertensive effect of the peptide was dependent on the peptide dosage from 0.1 to 10 mg of peptide/kg of body weight. The concentration of Tyr-Pro peptide increased during fermentation and reached about 8.1 micrograms/ml of whey in the pH 4.3 yogurt-like product. The antihypertensive peptide had a low inhibitory activity against angiotensin I-converting enzyme. The inhibition of 50% of the angiotensin I-converting enzyme (IC50) was 720 microM.

Administration, Oral↗