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Biomedical subjects

H Otani

Publications and source records attributed to H Otani.

At least 163 records · Page 9Linked to original sources
PubMed1993

Regulation of apolipoprotein B production and secretion in response to the change of intracellular cholesteryl ester contents in rabbit hepatocytes.

In the present study, we investigated the mechanisms that regulate apolipoprotein B-100 (apoB) secretion in response to the change of intracellular cholesteryl ester contents by adding low density lipoprotein (LDL) and an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase (pravastatin) in rabbit hepatocyte culture system. LDL caused a significant dose-dependent increase in apoB secretion. On the other hand, the addition of pravastatin decreased apoB secretion significantly. LDL caused a dose-dependent increase in cellular cholesteryl ester, while cellular cholesteryl ester was decreased by pravastatin significantly. Therefore, these results indicate that the change of apoB secretion was in parallel with the change of cellular cholesteryl ester contents. Cellular contents of free cholesterol, triglyceride, and phospholipid did not change. To investigate intracellular degradation of apoB prior to secretion, pulse-chase experiments were performed. It was shown that the addition of pravastatin accelerated intracellular degradation of apoB, while LDL slowed the apoB intracellular degradation rate. We also investigated whether the change of cellular cholesteryl ester could affect the apoB mRNA level. Northern blot analysis and solution hybridization RNase protection assay demonstrated that neither LDL nor pravastatin caused a significant change in cellular apoB mRNA level. We conclude that intracellular cholesteryl ester contents play a critical role in apoB secretion, and the intracellular apoB degradation rate could be the main mechanism that regulates apoB secretion in response to the change of intracellular cholesteryl ester level.

Acetates↗
PubMed1993

A novel family of retrotransposon-like elements in Xenopus laevis with a transcript inducible by two growth factors.

A cDNA clone named 1A11 was isolated in a screen for genes that are activated by both mesoderm inducing factors FGF and activin in animal explants of Xenopus laevis embryos. In undisturbed embryos, 1A11 is expressed during the gastrula stage in the entire marginal zone where mesoderm originates, and later in the somites, the tailbud, and at much lower levels in lateral mesoderm. The 1A11 sequence of 4.5 Kb has a 220 bp repeat at its ends, indicative of a retrotransposon-like structure. A long open reading frame encodes a predicted protein with only short homologies to the gag and protease regions of retroviruses and retrotransposons. Multiple copies of 1A11-related sequences were found in the Xenopus genome, constituting solo LTRs (long terminal repeats) of 1267 bp, and unique region copies (i.e., sequences internal to the repeats in the cDNA). Inverted repeats of 5 bp and apparent target site duplications of 5 bp surround the sequenced solo LTR. Thus, 1A11 is a new retrotransposon-like element in Xenopus laevis.

Activins↗
PubMed1993

Differential induction of regulatory genes during mesoderm formation in Xenopus laevis embryos.

Mesoderm development in Xenopus laevis depends on inductive cell interactions mediated by diffusible molecules. The mesoderm inducer activin is capable of redirecting the development of animal explants both morphologically and biochemically. We have studied the induction of four regulatory genes, Mix. 1, goosecoid (gsc), Xlim-1, and Xbra in such explants by activin, and the influence of other factors on this induction. Activin induction of gsc is strongly enhanced by dorsalization of the embryo by LiCl, while expression of the other genes is only slightly enhanced. The protein synthesis inhibitor cycloheximide (CHX) inhibits the activin-dependent induction of Xbra partially, while induction of Mix. 1 and Xlim-1 is essentially unaffected. In contrast, gsc shows strong superinduction in the presence of activin and CHX, and can be induced in animal explants by CHX alone. Induction and superinduction by CHX have previously been observed for immediate early genes in a variety of systems, notably for the activation of c-fos expression by serum stimulation, but have not been reported in early amphibian embryos.

Activins↗
PubMed1993

Expression of LIM class homeobox gene Xlim-3 in Xenopus development is limited to neural and neuroendocrine tissues.

The Xenopus LIM class homeobox gene Xlim-3 was identified initially as a fragment isolated by polymerase chain reaction cloning with an embryonic cDNA library as template (Taira et al., 1992, Genes Dev. 6, 356-366). cDNA clones representing most of the Xlim-3 mRNA were isolated from an adult brain library. The predicted Xlim-3 protein contains two copies of the LIM domain, a homeodomain, and a C-terminal region rich in proline, glycine, and serine. RNA blot hybridization showed that Xlim-3 mRNA is detected in dorsal regions at neural tube and tailbud stages and in adults predominantly in the pituitary gland and weakly in the eye and brain. Whole mount in situ hybridization revealed that Xlim-3 mRNA is first detectable at the neural plate stage in the stomodeal-hypophyseal (pituitary) anlage and in the neural plate where labeled cells were found adjacent to the forming floor plate. In situ hybridization analysis on serial sections at later stages showed that embryonic Xlim-3 expression persists in the pituitary and pineal, as well as in some cells of the retina, hindbrain, and spinal cord. In the retina, Xlim-3 mRNA was only detected in a distinct sublamina of the inner nuclear layer, but not in dividing cells of ciliary margin. This discrete manner of Xlim-3 expression, especially persistent expression in the pituitary (before morphogenesis of the gland to adult), supports a role in the specification and maintenance of differentiation of distinct neuronal and neuroendocrine tissues.

Amino Acid Sequence↗
PubMed1993

Ultrastructure of the developing stomach in human embryos.

Ultrastructural development of the stomach was studied by light, scanning electron and transmission electron microscopy, using 19 human embryos at Carnegie stages from 14 to 23 (6.8-28.0 mm in crown-rump length, 5 to 8 weeks of gestation). The precise time of appearance of differentiated characteristic structures was examined electron microscopically. The first gastric pit, with radially arranged epithelial cells beneath which the basement membrane bulged into the mesenchyme, was observed on the lesser curvature at stage 22. Although the mesenchymal condensation which would develop into the inner circular muscle layer appeared at stage 18 onward, cytoplasmic myofibrils were not observed until stage 22. Nerve fibers were first observed at stage 16, and at later stages they gathered into bundles to form a nerve plexus external to the developing inner circular muscle layer. On the basis of accurate timing of the appearance and the mode of development of these structures, possible relations between developing gastric layers were discussed. Histocytochemically, glycogen or other carbohydrates were demonstrated in the cytoplasm of the gastric epithelium throughout the stages examined. These carbohydrates were localized mainly in vacuole-like spaces in the basal part of the epithelial cells. This subcellular localization, and the amount of carbohydrate, did not change significantly during the observed embryonic period. In the serosa, carbohydrates were not detected at stages 14 and 15, but observed consistently within the vacuoles in the cytoplasm from stage 17 onward. No other layer of the embryonic stomach had detectable carbohydrates.(ABSTRACT TRUNCATED AT 250 WORDS)

Embryo, Mammalian↗
PubMed1993

99mTc-HMDP accumulation in a phyllodes tumor of the breast, a case report.

In a patient with breast tumor, 99mTc-HMDP accumulation in the tumor was recognized in evaluating bone metastasis. Surgery and histopathology revealed that the tumor was a phyllodes tumor. This scintigraphic finding was thought to be rare and phyllodes tumor should be included in differential diagnosis when 99mTc-HMDP accumulation in the breast was recognized.

Breast Neoplasms↗
PubMed1993

Locus of control and implicit memory.

Two experiments were conducted to investigate the influence of locus of control on implicit and explicit memory. We hypothesized that internals would rely on semantic processing, externals on perceptual processing. In Experiment 1, 80 college students studied 36 words and completed an implicit memory test in either a consistent or cross-modality condition. The results revealed that externals had higher priming scores than did internals, regardless of modality. In Experiment 2, 80 college students took either an implicit or explicit test. The results again revealed that externals showed higher priming scores than internals. The higher priming scores exhibited by the externals do not necessarily mean that they are more perceptually oriented than the internals are.

Adult↗
PubMed1993

[Chloride channels in cardiac muscle].

This section describes properties, signal transduction pathways for activation and the physiological roles of cardiac Cl- channels. Recent application of patch clamp technics have revealed that a wide variety of Cl- channels are present in cardiac cells, which are regulated by different cellular stimuli, such as alpha 1- or beta-adrenoceptor stimulation, ATP, adenosine and cell swelling. When these channels are activated, Cl- is transported ECl-dependently in both inward and outward directions, affecting the action potential durations and/or resting potentials. Analysis of cardiac Cl- channel mechanisms yields new aspects for understanding pathophysiological bases of heart diseases or arrests such as arrhythmia.

Chlorides↗
PubMed1993

Regulatory interactions during embryogenesis in Xenopus laevis.

During amphibian embryogenesis, axis definition and the specification of the mesoderm and neural plate depend on cell interactions. These interactions are mediated by peptide growth factors and other diffusible molecules including retinoic acid (RA). Several genes encoding transcription factors are known to be immediate early or delayed early responses to the action of growth factors and retinoids in the embryo. By the criterion of cycloheximide (CHX) resistance, goosecoid (gsc), Xlim-1, Xbra, Mix.1, XFKH1/pintallavis/XFD1, and Xnot are immediate early response genes in mesoderm/induction. Among these, gsc, Xnot and XFKH1 are superinduced by CHX, suggesting that their regulation depends in part on rapid turnover of the mRNA. RA is known to induce Xlim-1 in Xenopus embryos and to lead to anterior malformations. We show that 9-cis RA, the ligand of the RXR receptor class, is more effective than all-trans RA in generating these biological effects.

Animals↗
PubMed1992

Interleukin (IL)-2 and IL-3 induce distinct but overlapping responses in murine IL-3-dependent 32D cells transduced with human IL-2 receptor beta chain: involvement of tyrosine kinase(s) other than p56lck.

We have established IL-3-dependent 32D myeloid progenitor cells stably expressing the human IL-2 receptor beta chain (IL-2R beta). Whereas parental 32D cells proliferated only in response to IL-3, the transduced cells also proliferated in response to IL-2. Transduced cells expressed high- and intermediate-affinity IL-2Rs, resulting from expression of human IL-2R beta and murine IL-2R alpha chain (IL-2R alpha). IL-2 induced phenotypic changes not induced by IL-3, including the upregulated expression of endogenous murine IL-2R alpha and IL-2R beta and an increase in cell size. Therefore, the transduced IL-2R beta was not merely coupling with the IL-3 signaling pathway. IL-3 augmented several IL-2-induced responses including the up-regulation of IL-2R alpha. Both IL-2- and IL-3-induced proliferation and IL-2 induced IL-2R alpha expression were inhibited by the tyrosine kinase inhibitor herbimycin A. Thus, both IL-2- and IL-3-mediated effects required tyrosine kinase activity. The identity of the tyrosine kinase(s) mediating the IL-2 signals in these cells is not known but cannot be p56lck, a tyrosine kinase found in T cells, since 32D-IL-2R beta cells do not express p56lck.

Animals↗
PubMed1992

Supra-neuroectodermal cells and fibers on the primary nasal cavity and in the fourth ventricle of mouse and human embryos: scanning and transmission electron microscopic studies.

Neuroectoderm-derived epithelia of the primary nasal cavity and the fourth ventricular floor and roof were observed by scanning (SEM) and transmission electron microscopy (TEM) and SEM-TEM correlative views in mouse embryos of 9th to 13th days of gestation, and in 38 externally normal human embryos ranging at Carnegie stages from 13 to 18 (about 5 to 7 weeks of gestation). Smooth-surfaced spindle-shaped cells with one or more cytoplasmic processes and cord-like cytoplasmic structures were observed by SEM on the wall of the primary nasal cavity of both species. They had morphological features similar to those of neuronal type 1 supraependymal (SE) cells and SE fibers on the floor and roof of the fourth ventricle in both species. Type 1 SE cells, SE fibers, and corresponding structures in the primary nasal cavity were localized in relation to the underlying developing nerve and vascular systems. Furthermore, their processes and fibers ran roughly parallel to these underlying structures and they penetrated the epithelial layer at the ends, suggesting a connection with underlying structures. From TEM and SEM-TEM correlative observations, SE fibers in the fourth ventricle and cord-like structures in the primary nasal cavity, both with a larger diameter, were deduced as single axon-like processes or bundles of processes. Those fibers and cord-like structures of smaller diameters were interpreted as elongated telophase bridges; both contained parallel packed microtubules and connected distant cells. Since these processes and fibers were generally longer and became fewer at later developmental stages, they appeared to be transient neuronal structures. They may play a development-related role in such morphogenetic cell movements as in the developing nerve and vascular systems in the epithelial and/or subepithelial layers, but not as direct rudiments of adult nerve tissues.

Animals↗
PubMed1992

Interleukin (IL)-2 activation of p21ras in murine myeloid cells transfected with human IL-2 receptor beta chain.

The T cell growth factor interleukin-2 (IL-2) induces p21ras activation in T lymphocytes. To determine whether the IL-2 receptor (IL-2R) can regulate p21ras when expressed in a non-T cell environment we have examined the ability of IL-2 to activate p21ras in 32D murine myeloid progenitor cells transduced with human IL-2R beta chains. These cells are denoted beta 53 cells. 32D cells normally proliferate in response to IL-3 but the expression of the IL-2R beta chain confers IL-2 responsiveness to the cells. Our data show that IL-3 is able to activate p21ras in the parental 32D cells and both IL-2 and IL-3 can stimulate p21ras in the IL-2R-expressing beta 53 clone of 32D. In T lymphocytes, activation of protein kinase C (PKC) with phorbol esters is sufficient to stimulate p21ras. However, in 32D and beta 53 cells activation of PKC with phorbol esters does not result in p21ras activation even though these cells express functional PKC. It appears, therefore, that a PKC-mediated pathway for p21ras regulation exists in T lymphocytes but not in 32D cells. The IL-2R can couple to p21ras independently of the concomitant presence of the PKC pathway for p21ras regulation. These data imply that multiple intracellular mechanisms may exist to regulate p21ras and that cells of different lineages may differ with regard to p21ras regulation.

Animals↗
PubMed1992

Different patterns of protein kinase C redistribution mediated by alpha 1-adrenoceptor stimulation and phorbol ester in rat isolated left ventricular papillary muscle.

1. In rat left ventricular papillary muscle, phenylephrine, an alpha 1-adrenoceptor agonist, had a staurosporine-sensitive positive inotropic effect and increased the particulate-associated protein kinase C (PKC) activity without significant changes in total PKC activity or in cytosolic Ca2+/phospholipid-independent kinase (PKI) activity. 2. A PKC stimulant, phorbol 12,13-dibutyrate (PDBu), decreased contractility and slightly increased PKC activity in the particulate fractions, with a marked decrease and increase in total PKC and PKI activities, respectively. 3. The PDBu-induced negative inotropic response was attenuated by two protease inhibitors, leupeptine and a microbial peptide isolated from Aspergillus japonicus (E-64), which are known to inhibit the conversion of particulate-associated PKC to PKI. 4. Such differences in the patterns of PKC redistribution, i.e. marked increases in particulate PKC and cytosolic PKI activities caused by phenylephrine and PDBu, respectively, may account for the opposite inotropic effects of PKC stimulation by an alpha 1-agonist and a phorbol ester.

Adrenergic alpha-Agonists↗
PubMed1992

Age differences in perception of risk.

Age differences in perception of risk and the likelihood of disregarding warning signs were examined. A total of 358 adults, between 18 and 85 years old, were asked to rate 12 warning labels with respect to (a) how risky it would be to ignore the warning, (b) how likely it was that they would disregard the warning, and (c) how familiar they were with the labels. The older groups indicated higher risk in ignoring the signs than did the younger group. The older subjects were also less willing to disregard the signs than the younger subjects.

Adolescent↗
PubMed1992

The role of oxidized lipoproteins in the pathogenesis of atherosclerosis.

1. Oxidized low density lipoprotein (LDL) has been suggested to play an important role in atherogenesis by facilitating the accumulation of lipids in macrophages. In vitro studies from this laboratory have shown that oxidized LDL is recognized not only by the specific receptor for it, but also by the receptor which is common for oxidized LDL and acetyl LDL. Probucol, originally developed as an antioxidant, prevents the oxidative modification of LDL in vitro. Recent studies by the authors show that probucol prevents the progression of atherosclerosis in homozygous Watanabe heritable hyperlipidaemic rabbits in vivo without any changes in plasma LDL cholesterol levels. 2. These results strongly suggest that oxidative modification of LDL could occur in vivo and probucol could slow the progression of atherosclerosis, without changes in plasma cholesterol levels. 3. In addition, recently the authors demonstrated that high density lipoprotein (HDL) particles are also oxidized. Once HDL particles were oxidized, they showed a lessened effect on the decrease of cholesteryl ester in foam cells, suggesting oxidative modification of HDL may stimulate development of atherosclerosis by limiting efflux of cholesterol from foam cells. Moreover, HDL particles from probucol-treated patients are hardly oxidized; subsequently, these HDL particles caused a marked efflux of cholesterol from foam cells.

Animals↗
PubMed1992

[Relationship between venous invasion and hematogenous metastasis in the colorectal cancer patients].

We investigated the correlation between venous invasion and hematogenous metastasis. In thirteen patients with colorectal carcinoma, depth of invasion (ss.s or a1.a2) was the same. Four cases had hepatic metastasis at operation (group A), 3 cases were identified with hematogenous recurrence after operation (group B), and 6 cases were disease free over 10 years after operation (group C). Specimens were all step-sectioned and serial sections were stained both with HE and EM. Results were as follows. 1. Venous invasion was found in all cases and average rates of venous invasion (ARVI) of groups A and B were higher than that of group C (A; 7.8%, B; 6.3%, C; 2.1%, p less than 0.05). 2. In ss.s layer, ARVI of group A and B were higher than that of group C (A; 6.1%, B; 6.2%, C; 1.5%, p less than 0.05). 3. Rates of venous invasion to larger veins (diameter greater than 200 microns) were higher in group A than in others (A; 53.5%, B; 25.6%, C; 7.9%, p less than 0.05), and those to the middle-sized veins (diameter; 50-200 microns) were higher in group B than in others. These facts suggest that cancer invasion to the veins located in ss.s (a1.a2) layer or ranged in diameter over 200 microns relates to hematogenous metastasis.

Colorectal Neoplasms↗
PubMed1991

Host recognition by toxigenic plant pathogens.

Certain fungal pathogens release host-selective (or host-specific) toxins (HST) as a host recognition factor during spore germination at the infection site on plants. Prior to penetration of the pathogen into its host, the released toxin specifically binds to a putative receptor on the host cells and initiates signaling mechanisms leading to pleiotropic effects on cells. Of these, the crucial one negates the general and inducible defense reactions of the cells. This is accomplished by a signal from the HST, which is transduced through a path way at or near the step of plasma membrane modulation, which is directly or indirectly triggered by the HST. This mechanism operates even though the toxin may affect mitochondria or chloroplasts as the primary target organelle. The fungal spore is able to penetrate the so-called 'narcotized cell' and completes the initial colonization of the host. The host recognition process may take place without necessitating host cell death, even in the case of perthophytic parasites. At the molecular level, HST-mediated recognition of the host by a pathogen requires strict stereochemical precision like a lock and key.

Amino Acid Sequence↗