Biomedical subjects

H Naora

Publications and source records attributed to H Naora.

At least 37 records · Page 2Linked to original sources

PubMed1995

Differential expression patterns of beta-actin mRNA in cells undergoing apoptosis.

Microfilaments play an important role in the formation of apoptotic bodies. This study examined expression patterns of beta-actin, a key component of microfilament, during apoptosis. The data suggest that continuous beta-actin expression is not required for formation of apoptotic bodies. beta-actin mRNA levels rapidly declined in HL-60 cells following induction of apoptosis by actinomycin D, but were transiently elevated by two other apoptosis-inducing agents, cycloheximide and ionophore A23187. Furthermore, changes in beta-actin mRNA levels were less marked in U937 cells in which apoptosis was also induced by actinomycin D, as well as in WISH cells which demonstrated no typical apoptotic characteristics following actinomycin D treatment.

Actins↗

PubMed1995

Apoptosis as a mechanism of skin renewal: Le(y)-antigen expression is involved in an early event of a cell's commitment to apoptosis.

Skin renewal is a typical example of the active participation of a cell in its own death process. Cells arising from mitotic activity in the stratum germinativum of the epidermis continuously migrate upwards to the stratum corneum, where dead cells are eventually desquamated. Recent studies have suggested that apoptosis is involved in the dynamic process of skin renewal. However, this still remains to be further elucidated. In this paper, we investigated the involvement of apoptosis in the skin renewal process. Changes in the morphology of cells in different epidermal layers were compared with histochemical analyses of the extent of DNA fragmentation, as determined by nick end-labelling, and of the reactivities to a monoclonal antibody directed to Le(y)-antigen, difucosylated type 2 chain determinant, which has a close association with apoptosis, and to a monoclonal antibody directed to the proliferating cell nuclear antigen. The results show that apoptosis proceeds concomitantly with cell movement in the epidermis. It seems likely that commitment of a cell to death by apoptosis occurs in the epidermal tissue immediately after completion of cell proliferation, and that Le(y)-antigen expression may be involved in the entire apoptotic process including this early event.

Aged↗

PubMed1995

Opaque eyes developed in transgenic mice with T-cell receptor delta gene.

PURPOSE: During the generation of transgenic mice (TGs) introduced with mouse T-cell receptor delta (TCR delta) gene, the authors found a TG line with corneal opacity that coincided with the presence of the transgene. The authors investigated the pathogenesis and molecular mechanisms of this corneal opacity in this line. METHODS: The pathologic features and pathogenesis of the corneal opacity in TGs were examined histologically using transmission and scanning electron microscopy, as well as light microscopy. DNA and RNA blot analyses were performed to examine the copy number and the expression of the transgenes, respectively. RESULTS: Histologically, edema of the corneal epithelium and adhesion of the iris to the cornea were observed in adult TGs. In the developmental analysis, the authors first observed relative hypoplasia of the ciliary body on day 18 of gestation and dysgenesis of the anterior chamber angle from postnatal day 2. Corneal opacity was observed from postnatal day 8, coinciding with the histologic vesicular change of the epithelium. No inflammation was observed through its life. In the sublines that have different copy numbers of the transgene, the occurrence of the opacity depended on the copy number of the transgene. Expression of the transgene in the thymus was consistent with the number of the introduced transgene. CONCLUSION: In a TCR delta TG line, the overexpression of transgenes coincided with abnormal development of the ocular anterior segment and the corneal opacity. Pathogenesis is described, and possible molecular mechanisms are discussed.

Animals↗

PubMed1995

Comparison of the mechanisms regulating IL-5, IL-4, and three other lymphokine genes in the Th2 clone D10.G4.1.

The selective eosinophilia characteristic of asthma and parasite infections appears to be dependent on the production of interleukin-5 (IL-5) by activated T lymphocytes; however, little is known about IL-5 gene regulation. In the present study, a comparison was made of the basic mechanisms regulating mRNA levels for IL-5 and four other lymphokines that are coordinately expressed in the Th2 clone D10.G4.1 in response to concanavalin A (Con A) stimulation. Northern blot and nuclear run-off analyses indicated that IL-5 and IL-4 mRNA levels are primarily regulated at the transcriptional level. Regulation of IL-3, IL-6, and IL-10 mRNA levels involved control of mRNA stability and transcription. These three mRNAs were stabilized by cycloheximide (CHX). De novo protein synthesis was obligatory for IL-5 gene transcription and was also required for maximal transcription of the IL-4 and IL-10 genes. Expression of the IL-5, IL-6, and IL-10 genes was resistant to cyclosporine A (CsA), whereas IL-3 and IL-4 gene expression was completely inhibited, indicating the involvement of different signalling pathways in the regulation of these genes. The results indicate that the IL-5 gene and each of the other genes studied are independently regulated, providing the possibility of non-coordinate expression in vivo depending on the nature of the signals received during T cell activation.

Animals↗

PubMed1995

Association of nbl gene expression and glucocorticoid-induced apoptosis in mouse thymus in vivo.

A gene of unknown biological function, nbl, was originally isolated by virtue of its abundance in a Namalwa Burkitt Lymphoma cDNA library. nbl expression was initially found to be higher in tissues which exhibited internucleosomal DNA cleavage characteristic of apoptosis, than in tissues which did not exhibit a 'DNA ladder'. nbl expression was therefore examined in mouse thymus in vivo, in which apoptosis is induced by the glucocorticoid, dexamethasone. nbl expression was markedly enhanced by dexamethasone treatment and then sharply decreased prior to the occurrence of maximal 'DNA ladder' formation. In contrast, expression of myc, which is believed to be involved in apoptosis in other cell systems, declined as thymic apoptosis increased. Thymic apoptosis was blocked by the transcriptional inhibitor actinomycin D, if administered when nbl expression was enhanced, but not before or after the peak of nbl expression. These results suggest that nbl expression is associated with thymic apoptosis.

Animals↗

PubMed1995

The effects of PSK, a biological response modifier, on congenital ocular abnormalities induced by X-ray irradiation.

The antiteratogenic effects of PSK, a biological response modifier, were examined using histological and developmental analysis. The whole bodies of pregnant mice were irradiated with X-rays and injected with PSK within ten minutes after irradiation on day 7 of gestation (E7). The foetuses on E18 were examined and a high incidence of malformations were observed in X-ray irradiated embryos. Microphthalmia was the most frequent malformation. PSK administration suppressed the X-ray irradiation-induced ocular anomalies in not only the frequency, as deduced by external observation, but also in histopathological changes in the retina, lens, and cornea. In particular, the incidence of lens aplasia was significantly decreased by PSK administration. Developmental analysis using E10 and E13 embryos revealed that the decrease in the incidence of histopathological changes was first observed within 72 hours after PSK administration. In addition, X-ray irradiation-induced early foetal death (E10-13) was also suppressed by PSK administration. The possible mechanisms of the antiteratogenic effects of PSK are discussed.

Abnormalities, Radiation-Induced↗

PubMed1994

Functional role and signal-induced modulation of proteins recognizing the conserved TCATTT-containing promoter elements in the murine IL-5 and GM-CSF genes in T lymphocytes.

The TCATTT-containing element extending from -61 to -41 of the mouse IL-5 gene is highly conserved in the corresponding region of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene and has been previously shown to be involved in regulating inducible GM-CSF gene expression. By using stable transfection assays in the mouse Th2 clone D10.G4.1, we show that the TCATTT-containing element is also involved in the regulation of inducible IL-5 gene expression. The mouse IL-5 and GM-CSF homologues of this element were found by gel shift analysis to form DNA-nuclear protein complexes of similar electrophoretic mobility under conditions in which expression of these genes is induced. However, comparative studies using extracts of D10.G4.1 cells treated with the cellular activators Con A and PMA and the inhibitors cycloheximide and cyclosporin A indicated that the binding activities to the conserved elements in the IL-5 and GM-CSF genes (designated NF-IL-5A and NF-GM-CSFA, respectively) are regulated by different signaling pathways. In addition, NF-IL-5A is not induced in the Th1 clone HDK-1 which does not express the IL-5 gene. The strong correlation between the signal-dependent and cell-specific modulation of IL-5 and GM-CSF gene expression patterns and the binding activities of NF-IL-5A and NF-GM-CSFA suggests that these nuclear proteins are involved in the transduction of T cell activation signals to the transcriptional machinery of these genes through their interactions with their respective TCATTT-containing elements.

Animals↗

PubMed1994

TCR-dependent and -independent signaling mechanisms differentially regulate lymphokine gene expression in the murine T helper clone D10.G4.1.

The signaling mechanisms that regulate lymphokine gene expression in the murine Th2 clone D10.G4.1 were investigated by comparing the steady state mRNA levels of six lymphokine genes in response to cellular treatment with various activators and inhibitors of several key signaling pathways. A surprising degree of differential regulation was found. All of the genes studied (IL-3, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage (GM)-CSF) were induced by the lectin Con A and the TCR idiotype-specific mAb 3D3. However, the induction of the IL-3, IL-4, and GM-CSF genes, but not the IL-5, IL-6, and IL-10 genes, was strongly inhibited by cyclosporin A. Furthermore, IL-5, IL-6, and IL-10 genes were independently induced by IL-1 alpha, the phorbol ester PMA, and by forskolin, an activator of adenylate cyclase. Results of studies performed with use of the Ca2+ ionophore A23187 indicated that elevation of intracellular Ca2+ levels is sufficient to fully induce IL-3 and IL-4 gene expression. Protein kinase C activation was also required for full induction of the GM-CSF gene and seemed to be obligatory for maximal IL-5 gene expression. The patterns of mRNA induction by the different stimuli broadly correlated with increased rates of transcription. In addition to their induction by IL-1 alpha, the IL-5, IL-6, and IL-10 genes were also induced by mAbs to CD2 and to CD45. In contrast, adding CD45 mAb strongly inhibited the induction of IL-3, IL-4, and GM-CSF genes through TCR stimulation. These results indicate that distinct groups of lymphokine genes may be differentially regulated by signaling pathways that are activated by stimulation of the TCR and other cell surface molecules.

Animals↗

PubMed1994

Mechanisms regulating the mRNA levels of interleukin-5 and two other coordinately expressed lymphokines in the murine T lymphoma EL4.23.

The mechanisms that regulate the mRNA levels of interleukin-5 (IL-5) were compared with those regulating the mRNA levels of two other coordinately expressed lymphokines in the murine T lymphoma EL4.23. Our results indicate that IL-5 mRNA levels are independently regulated from those of IL-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNAs. The induction of IL-5 mRNA by phorbol 12-myristate 13-acetate (PMA) stimulation was found to be cyclosporin A-resistant, in contrast to the induction of IL-2 and GM-CSF mRNAs. Although the three lymphokine mRNAs were not detected in unstimulated cells by Northern blot analysis, the GM-CSF gene was found by nuclear run-off analysis to be constitutively transcribed. However, the IL-2 and IL-5 genes were transcriptionally inactive in the absence of PMA stimulation. The induction of IL-5 mRNA by PMA stimulation primarily involved increased transcriptional activity. In contrast, GM-CSF mRNA induction predominantly involved enhanced mRNA stability. Both transcriptional and mRNA stabilization mechanisms appeared to regulate IL-2 mRNA induction. The activation of IL-2 and IL-5 gene transcription was dependent on de novo protein synthesis. Cellular treatment with cycloheximide enhanced IL-2 gene transcription once activation was initiated, implicating the involvement of a labile repressor(s). Furthermore, IL-5 mRNA was more stable than IL-2 and GM-CSF mRNAs. These latter two species were stabilized by cycloheximide, suggesting that a labile mechanism may regulate their degradation.

Animals↗

PubMed1994

Transgenic mouse model of hemifacial microsomia: cloning and characterization of insertional mutation region on chromosome 10.

The 643 transgenic mouse line carries an autosomal dominant insertional mutation that results in hemifacial microsomia (HFM), including microtia and/or abnormal biting. In this paper, we characterize the transgene integration site in transgenic mice and preintegration site of wildtype mice. The locus, designated Hfm (hemifacial microsomia-associated locus), was mapped to chromosome 10, B1-3, by chromosome in situ hybridization. We cloned the transgene insertion site from the transgenic DNA library. By using the 5' and 3' flanking sequences, the preintegration region was isolated. The analysis of these regions showed that a deletion of at least 23 kb DNA occurred in association with the transgene integration. Evolutionarily conserved regions were detected within and beside the deleted region. The result of mating between hemizygotes suggests that the phenotype of the homozygote is lethality in the prenatal period. These results suggest that the Hfm locus is necessary for prenatal development and that this strain is a useful animal model for investigating the genetic predisposition to HFM in humans.

Animals↗

PubMed1994

Gene ecology: a cis-acting gene-to-gene interaction due to the spatial arrangement of genes in chromosomes affects neighbouring transfected c-H-ras expression.

A cis-acting interference between gene activities, which occurs when two genes lie on the same DNA strand and have an intergenic distance less than a defined length, was previously deduced when chromosomal organizations of various higher eukaryote nuclear genes in clusters were compared. In order to investigate such an interference due to arrangement of genes along chromosomes, we have isolated a few cell lines which possessed (i) human mutated c-H-ras fused with the mouse mammary tumour virus long terminal repeat and (ii) the E. coli xanthine-guanine phosphoribosyltransferase (gpt) gene with the SV40 promoter, on the same or on different DNA strands, separated by a short intergenic distance or unlinked. Since the cancerous phenotype of a cell can be readily identified due to c-H-ras expression, we examined in these cell lines whether continuous c-H-ras expression, induced by dexamethasone, is disturbed through a cis-acting gene-to-gene interaction when the expression of the neighbouring gpt gene is enforced and as a result, the cancerous state of a cell is converted to the 'normal' state. The enforced expression of the neighbouring gpt gene was shown to alter c-H-ras expression, and thus reversible conversion of a cell between cancerous and normal states occurred only when the cell possessed an optimum number of the gene pair, in which both c-H-ras and the gpt gene were on the same DNA strand. This implies that the spatial arrangement of genes in chromosomes plays an important role in the regulation of gene expression in a cluster.

Animals↗

PubMed1992

Morphology of the kidney of the platypus (Ornithorhynchus anatinus: Monotremata).

The platypus kidney shows morphological similarities to those of other mammals. Macroscopically, the cortex is easily distinguishable from the fairly wide medulla. Within the medulla, no clear border is observed between the inner and outer zones. Light and transmission electron microscopically, the glomeruli show quite similar architecture to those of other mammals; however, the glomerular lobulation is very clear. The glomerular tufts are rather simple, but capillary lumen varies widely in size, which is one of the unique features of the platypus kidney. The urinary tubule is generally similar to that of human and other mammals in shape and segmentation; however, the staining specificities of histochemical reactions and the shape of epithelial cells of the Henle's loop differ from those of other mammals. The most conspicuous features are: 1) although no protein casts are found in the tubular lumina, epithelial cells of the proximal convoluted tubule (PCT) have numerous electron-dense vesicles as in human nephrotic kidneys; and 2) the platypus Henle's loop consists of the thick epithelial cells similar to the mammalian type nephron of birds. As compared to those of other mammals such as humans and rats, our observations suggest that the platypus kidney is less developed, in terms of evolution.

Animals↗

PubMed1991

An optimum dose of c-H-ras is a prerequisite for hormone-dependent conversion of a cell between cancerous and normal states in tissue culture.

We have established a few cell lines which can be reversibly converted from cancerous to normal and vice versa by the addition to, or removal from the culture medium of glucocorticoid hormone. These cell lines were derived from mouse NIH 3T3 cells and possessed the integrated gene pairs on chromosomes, which are composed of human mutated c-H-ras fused with mouse mammary tumour virus long terminal repeat and E. coli xanthine-guanine phosphoribosyltransferase gene with the SV40 promoter. We have characterised these cell lines in order to elucidate an essential requirement for the conversion of the state of a cell. It was found that the presence of at least two to three copies of the gene pair per diploid genome are essential. An approximate threshold level of c-H-ras 1.6 kb RNA required for reversible conversion was estimated.

Animals↗

PubMed1991

Chromosome analysis of postimplantation stage embryos for studying possible causes of developmental abnormalities in nonobese diabetic mice.

The chromosomes of postimplantation stage embryos of nonobese diabetic (NOD) mice were analyzed to investigate the causal mechanism of congenital anomalies in diabetic pregnancies. Postimplantation stage embryos (day 12 of gestation) in diabetic (NOD-DM) and nondiabetic (NOD-N) NOD mice had either a high or low incidence of chromosomal abnormalities. A large majority of externally normal embryos from NOD-DM and NOD-N mice had low incidences. A high incidence of chromosomal abnormalities was found in externally abnormal embryos of NOD-DM and NOD-N mice, and in a smaller number of externally normal NOD-N and NOD-DM embryos. No control ICR embryo manifested a high incidence of chromosomal abnormalities. In the NOD-DM embryos, the chromosomes appeared to be influenced by long-term maternal diabetic conditions, while high incidences of chromosomal abnormalities in the NOD-N embryos suggested a probable cause by other factor(s) (e.g. a genetic predisposition) or by a very mild diabetic condition because the NOD-N mice were prediabetic.

Animals↗

PubMed1991

Diabetic environment and genetic predisposition as causes of congenital malformations in NOD mouse embryos.

Congenital malformations such as neural tube defects and a kinky or waved vertebral column were observed at higher incidence in embryos from nonobese diabetic (NOD) female mice with overt diabetes (NOD-D; 40.3%, P less than 0.005) or without overt diabetes (NOD-N; 8.4%, P less than 0.05) than in control Institute of Cancer Research (ICR) mouse embryos (1%) at day 13 of gestation. In vivo and in vitro preimplantation development of NOD-N, NOD-D, and ICR embryos did not differ in rate of development, size, or morphology. Embryos cultured from one-cell to early blastocyst stage were mutually transferred to uterine horns of pseudopregnant females between NOD-D and ICR mice and examined at day 13 of gestation. There were significant decreases in ratios of implantation and of viable embryos in ICR embryos transferred to NOD-D recipients (52%, P less than 0.001 and 14%, P less than 0.001, respectively) compared with those ratios in ICR embryos transferred to ICR uteri (79.2 and 56.2%) or those in NOD-D embryos transferred to ICR uteri (70.3 and 33.1%). Furthermore, 18 of 45 viable ICR embryos transferred to NOD-D dams had malformations, whereas there were no malformations in 73 viable ICR embryos transferred to ICR recipients, suggesting deleterious effects of maternal diabetic environment to embryos. On the other hand, 8 of 58 viable NOD-D embryos that were cultured in vitro and transferred to ICR uteri had malformations such as neural tube defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Intestinal mucosa and intra-abdominal lymphoid tissues of the platypus, Ornithorhynchus anatinus.

The morphological features of the intestinal mucosa and intra-abdominal lymphoid tissues of the platypus were examined. The mucosal surface of the intestine was characterized by the formation of large folds instead of the finger-like villi found in placental mammals. The lamina propria of the mucosal fold was well developed and contained numerous lymphocytes, expressing the lymphoid nature which is characteristic of the lamina propria of mammalian intestines. Although numerous well-developed Peyer's patches were observed in the ileum, solitary lymphoid nodules could not be found anywhere in the small intestine. Other intra-abdominal lymphoid tissues, particularly mesenteric lymphoid nodules, were well developed. However, each nodule represented a single follicle in contrast to the mammalian mesenteric lymph node which is composed of numerous follicles fused together. On the basis of the above findings, the tissues in question are considered to be at an evolutionary level preceding that of placental mammals.

Abdomen↗

PubMed1991

Microtia as an autosomal dominant mutation in a transgenic mouse line: a possible animal model of branchial arch anomalies.

Microtia was found in a transgenic mouse 643 and all offspring with microtia had the transgene. No anomalies, other than occasional low set ear and abnormal biting, were identified in other tissues and organs. In the developmental analysis, on the 9th and 10th days of gestation, hypoplasia of the second branchial arch was observed, while various kinds of malformed hillocks were noted on the 12th day. All of these anomalous embryos were transgenic. Histologically, hemorrhage and subsequent phagocytosis were noted at the second branchial arch. Left sided anomalies were predominant and in bilaterally defective ones asymmetry existed. These findings closely resembled to those in experimental animals with a phenocopy of the first and second branchial arch syndrome in humans. Since all other transgenic mouse lines with the same transgene as 643 appeared normal, this dysmorphic phenotype may be caused by an insertional mutation of a host gene, although inappropriate expression of the transgene should be examined further as a possible cause. These results suggest that this transgenic mouse line 643 may be useful as an animal model of branchial arch anomalies in humans.

Animals↗

PubMed1990

Development of the innervation pattern in the upper limb of staged human embryos.

The upper limb nerves of 8 human embryos (Carnegie stages 13-21) were studied by reconstruction. In stage 13, upper limb nerves (C5-T1) extended from the spinal cord. In stage 14, these nerves united to form the nascent brachial plexus. In stages 16 and 17, the median nerve, the radial nerve and the ulnar nerve entered into the hand plate. In stages 20 and 21, the upper limb nerves were observed in an orientation and arrangement similar to those in the adult.

Arm↗