Search PubMed⌕ Search

Biomedical subjects

J Piette

Publications and source records attributed to J Piette.

At least 145 records · Page 8Linked to original sources
PubMed1990

An in vivo model of varicella-zoster virus latent infection of dorsal root ganglia.

We describe here the first in vivo model of varicella-zoster virus (VZV) latent infection in the adult rat peripheral nervous system. Infected Mewo cells were injected subcutaneously along the spine of healthy adult rats. No clinical sign of infection was observed even 9 months after inoculation. Humoral immune response to VZV was detected in all infected animals throughout the study (9 months). The presence of viral material in dissociated and cultured dorsal root ganglia (DRG) from inoculated animals was studied by immunoperoxidase and in situ hybridization. When DRGs from infected animals were plated in culture from 1 month and up to 9 months after inoculation, viral nucleic acids and proteins were detected in neurons. Furthermore, trypsinization and subcultivation of infected neurons in culture is needed to reactivate infectious virus at least in some of the neurons. This model provides a useful tool for studying 1) the molecular mechanisms leading to an in vivo latency, 2) the role of the immune system, in particular cellular immunity, on the establishment, maintenance, and reactivation of latency, 3) the neurotropism of mutant viruses, and 4) the effects of antiviral agents.

Animals↗
PubMed1990

Acute and persistent varicella-zoster virus infection of human and murine neuroblastoma cell lines.

Human and murine neuroblastoma cell lines were infected in vitro with varicella-zoster virus (VZV). Infected human neuroblastoma cells (IMR-32) supported the synthesis of abundant viral antigens as detected by indirect immunoperoxidase labeling using human serum rich in anti-VZV antibodies and did not survive the infection. In situ hybridization (ISH) with VZV-cloned probes revealed a strong hybridization signal in these infected cells. During cultivation, the virus was released in the culture medium, and viral polypeptides were revealed by Western blotting of infected cells, using either a monoclonal anti-gpI antibody or a rabbit antiserum. All these findings indicate that IMR-32 cells support a productive and lytic infection by VZV, whether infected by cell-free virus or by cocultivation with infected cells. Murine neuroblastoma cells (neuro-2A) survived VZV infection and did not produce any infectious virus. No VZV-specific proteins were detected in infected cells either by immunolabeling or by Western blotting. However, viral nucleic acids could be detected by ISH, indicating that mouse neuroblastoma cells displayed a nonproductive, nonlytic infection. Infected neuro-2A cells have been examined by ISH using probes corresponding to immediate early (IE) genes 4, 62, and 63 and late (L) gene 31 encoding gpII. A strong hybridization signal was detected when infected cells were probed with a fragment containing the IE genes 62 and 63. Lower levels of hybridization were detected with the other probes, corresponding to IE or L genes. These systems allow comparative molecular analysis of persistent and acute infection of nerve cells by VZV.

Animals↗
PubMed1990

Induction of acetylcholine receptor alpha-subunit gene expression in chicken myotubes by blocking electrical activity requires ongoing protein synthesis.

The level of acetylcholine receptor alpha-subunit mRNA in primary cultures of chicken myotubes increases when the spontaneous electrical activity of the myotube is suppressed by the sodium channel blocker tetrodotoxin. This increase was prevented by two translational inhibitors: cycloheximide and anisomycin. Neither the basal level of alpha-subunit mRNA nor that of muscle-specific creatine phosphokinase mRNA was affected by these inhibitors. In contrast, cycloheximide potentiated the limited increase of alpha-subunit mRNA levels evoked by the neuropeptide calcitonin gene-related peptide. The high level of alpha-subunit mRNA elicited by tetrodotoxin treatment did not persist after subsequent addition of cycloheximide in the presence of tetrodotoxin, indicating that the continuous synthesis of protein factor(s) is necessary for this regulation. Moreover, cycloheximide decreased the high level of alpha-subunit mRNA present at early stages of in vitro maturation of muscle primary cultures without blocking the further increase of the muscle-specific creatine phosphokinase mRNA. Implications of the requirement for constant synthesis of protein factors on the induction of muscle-specific gene expression by blocking myotube electrical activity are discussed.

Animals↗
PubMed1990

Activation of human immunodeficiency virus type 1 by oxidative stress.

An important aspect of the infection by the human immunodeficiency virus (HIV-1) type 1 is its clinical latency, suggesting that the virus itself or the provirus may remain latent for extended periods of time after primary infection. Certain heterologous viral proteins or chemical and physical agents are able to reactivate latent virus. Since a common denominator shared by these agents is the ability to cause stress response in cells, we have examined the effects of oxidative stress mediated by hydrogen peroxide (H2O2) on HIV-1 latently infected promonocytic cell line termed U1. After exposure to H2O2 in concentrations ranging from 0.1 to 2 mM, the viability of the U1 cells decreased during 24 h before recovery. At 24 h post stress, the U1 cells began to express virus as assessed by elevated reverse transcriptase activities in culture supernatants. Immunofluorescence carried out on stressed U1 cells using anti-HIV-1 polyclonal antibodies showed that H2O2 leads to HIV-1 gene expression activation, but not to a release of viral particles from damaged cells. Additionally, using a HeLa cell line containing integrated the bacterial chloramphenicol acetyl transferase (CAT) gene under the control of the HIV-1 long terminal repeat (LTR), we have shown that oxidative stress mediated by H2O2 allows transactivation of the viral LTR revealed by intracellular CAT activity. A stimulation factor of around 4 of CAT activity can be reached when these cells are treated with 0.5 mM H2O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗
PubMed1990

A comparison of hospital and community case management programs for persons with AIDS.

To determine whether locus of AIDS case management affects the content of this service, a survey of case managers in 42 major American cities was conducted. One hundred seventy-one case managers working in both public hospitals and community-based organizations (CBOs) responded. Hospital case managers were substantially more likely to report clinical training than CBO case managers. Hospital case managers' case loads were more likely to include drug users and patients with more urgent needs such as housing and drug abuse treatment. While CBO case managers were more likely to work to develop services in the community, hospital case managers reported working more closely with medical staff and discharge planning committees. CBO case managers reported greater difficulty obtaining a number of key services for their clients including home health care, housekeeping, and entitlements; hospital case managers reported greater difficulty obtaining emotional support volunteers. These results indicate that locus of case management strongly affects the structure and content of this service. The importance of these findings for future program planning is discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Protein-binding elements in the promoter region of the mouse p53 gene.

p53 is a cellular protein whose expression plays a crucial role in the regulation of cell proliferation and of neoplastic processes. p53 mRNA levels in mouse fibroblasts can be elevated in response to TPA and to serum stimulation. The promoter region of the p53 gene contains a conserved element which is highly homologous to the consensus AP1 binding site (7/8 matching bases). This AP1-like site, denoted the PF1 site, confers upon a heterologous promoter ability to respond to elevated expression of c-jun. Furthermore, the PF1 site binds protein(s) in a specific and serum-induced manner. Unexpectedly, this factor is most probably not AP1, as evident from the inability of an authentic AP1 site to compete the binding efficiently, as well as from the failure of purified AP1 to bind to the PF1 site. Hence, PF1 may be a novel AP1-related transcription factor. In addition, the 5' region of the p53 gene also contains an NF1 binding site, whose location suggests a possible regulatory role.

Animals↗
PubMed1989

TNF stimulates expression of mouse MHC class I genes by inducing an NF kappa B-like enhancer binding activity which displaces constitutive factors.

We have dissected the mouse H-2Kb gene promoter in order to define the sequences responsible for induction by tumour necrosis factor (TNF-alpha). An enhancer element (-187 to -158) composed of two imperfect direct palindromic repeats has been shown to be necessary and sufficient for TNF-alpha induction of a heterologous promoter. A multimer of either repeat is also responsive, while a single copy is not: this is the situation in the beta 2-microglobulin (beta 2-m) promoter which contains a single palindrome and does not respond to TNF-alpha. We had previously found that the two repeats can bind a factor named KBF1. We show here that in the uninduced state the transcription factor AP2 binds to the interpalindromic region, while in TNF-treated cells an NF kappa B-like activity is induced which displaces both KBF1 and AP2 and binds to the two palindromes. This strongly suggests that induction of an NF kappa B-like activity is responsible for TNF-alpha stimulation of mouse MHC class I genes.

Animals↗
PubMed1989

Interaction of nuclear factors with the upstream region of the alpha-subunit gene of chicken muscle acetylcholine receptor: variations with muscle differentiation and denervation.

The region lying between nucleotides (nt) -110 and -45 of chicken acetylcholine receptor alpha-subunit gene 5' upstream sequence confers developmental control of expression in primary cultures of chicken myotubes. This region interacts with several nuclear factors present in muscle cells as shown by DNase I footprinting and gel-retardation experiments. An Sp1-like factor and a guanine stretch-binding protein were found to bind to overlapping sites immediately upstream of the TATA box. Several factors interacting in the same region with a domain similar to the SV40 enhancer core appeared during in vitro differentiation of myoblasts into myotubes. The concentration of some of these factors increased also after denervation of leg muscle in newborn chickens. The specific interaction of nuclear factors with this domain may thus play a critical role in the regulation of alpha-subunit gene expression by muscle differentiation and electrical activity.

Animals↗
PubMed1989

Varicella-zoster virus infection of adult rat sensory neurons in vitro.

We report here an in vitro model of neuronal infection by varicella-zoster virus (VZV). Such a model has been achieved by using dissociated adult rat dorsal root ganglia cells infected by cocultivation with VZV-infected MRC5 cells or with cell-free virus. Indirect VZV immunolabeling, in situ hybridization, and neuron-specific immunolabeling demonstrated that VZV infection occurred selectively in neurons. VZV-specific immunolabeling detected a few neurons 1 or 2 days postinfection but not later. Genome detection using cloned VZV DNA probes revealed a hybridization signal primarily with RNA. Within 1 to 6 days postinfection, a progressive increase of VZV-specific hybridization was observed in up to 50% of the neurons. RNAs corresponding to immediate-early, early, and late genes were found, and transcripts of immediate-early gene 63 were particularly abundant.

Animals↗
PubMed1989

Stimulation of protein kinase C or protein kinase A mediated signal transduction pathways shows three modes of response among serum inducible genes.

Activation of the signal transduction pathways mediated by protein kinase A (PKA) or protein kinase C (PKC) led to different responses of several serum inducible genes including the jun gene family, c-fos, c-myc, krox 20 and krox 24. Whereas all of these genes were stimulated by the phorbol ester TPA, a chemical activator of protein kinase C, they were differently regulated upon cAMP stimulation of the PKA dependent pathway. The proto-oncogenes jun B, c-fos, and to a lesser extent jun D were stimulated by increasing the intracellular concentration of cAMP, whereas the TPA stimulation of c-jun and c-myc was inhibited under these conditions. Krox 20 and krox 24 were insensitive to this second messenger. This study allowed us to classify these growth stimulated genes into three distinct groups distinguished by their sensitivity to elevated concentrations of intracellular cAMP. The inhibition of c-jun and c-myc expression in the presence of increased cAMP levels may be at least partially responsible for the growth inhibitory effect of this agent in Balb/c-3T3 cells.

Animals↗
PubMed1988

Molecular interactions in the control region of the carAB operon encoding Escherichia coli carbamoylphosphate synthetase.

The control region of the carAB operon, encoding carbamoylphosphate synthetase, comprises two tandem promoters (P1, upstream and P2, downstream) located 67 base-pairs apart and repressed respectively by pyrimidines and arginine. RNA polymerase and pure arginine repressor bind to the P2 region in mutually exclusive ways. Repressor protects the two adjacent palindromic ARG boxes overlapping P2 against DNase I. Binding of RNA polymerase to P1 is abnormal; the region protected against DNase I is shifted upstream by about 20 nucleotides with respect to the position expected from the transcription startpoint. This pattern is not due to interference with polymerase binding at P2, since it is observed also in the presence of repressor and on an isolated P1 region. Binding of RNA polymerase is relatively weak and heparin-sensitive suggesting that, in vivo, an ancillary factor is required to promote the formation of an open complex. S1 nuclease mapping experiments show that the simultaneous presence of pyrimidines and arginine represses the downstream arginine-specific promoter (P2) more efficiently than arginine alone. This effect is not due to a direct regulatory interaction between pyrimidines and P2, since it is not observed when P1 is inactivated by insertion mutations or partial deletion. It has been shown that transcription initiated at P1 can proceed even when arginine represses P2. We therefore suggest that P2 operator-arginine repressor complex is destabilized by RNA polymerase binding at P1 or transcription from P1. We describe a novel technique to select for expression-down mutants in a lac fusion context.

Bacterial Proteins↗
PubMed1988

Mutagenesis induced by site specifically placed 4'-hydroxymethyl-4,5',8-trimethylpsoralen adducts.

Closed circular double stranded M13mp19 DNA containing a site-specifically placed HMT (4'-hydroxymethyl-4-5'-8-trimethylpsoralen) monoadduct or crosslink was synthesized in vitro. The damaged DNA were scored for loss of infectivity by transfection into repair proficient or deficient E. coli and into SOS induced E. coli. Mutant phages were detected by the loss of alpha-complementation between the viral and the host Lac Z genes or by the acquisition of resistance to kpn I digestion. Our results indicate that HMT mutagenesis is targeted and that deletion or transversion of the modified thymidine is the predominant sequence change elicited by a monoadduct or a crosslink. Transfection of the monoadducted DNA into a Uvr A deficient strain did not change the mutation pattern but did increase the respective mutation frequencies. Transfection of the crosslinked DNA into a SOS induced host resulted in the appearence of other types of mutations attributable to an increase in both targeted and untargeted mutations.

Chromosome Deletion↗
PubMed1988

Singlet oxygen production and photoisomerization: two competitive processes for merocyanine 540 irradiated with visible light.

The quantum yields of singlet oxygen production by merocyanine 540 have been measured during visible light irradiation performed in methanol and ethanol. These appear to be one hundred times smaller than the quantum yield for rose bengal measured under the same conditions. Flash photolysis experiments demonstrate the ability of merocyanine 540 molecules to isomerize under visible light irradiation: the isomerization quantum yields are about 0.65 in both ethanol and methanol. This information combined with the fluorescence quantum yield data account for the low values for singlet oxygen production.

Isomerism↗
PubMed1988

Constitutive synthesis of activator protein 1 transcription factor after viral transformation of mouse fibroblasts.

Transcription factor activator protein 1 (AP1) interacts with the promoter region of a number of genes that are stimulated by growth factors present in serum or by agents such as phorbol 12-myristate 13-acetate (PMA) that partially mimic their action. To investigate the possible role of AP1 in the control of cellular growth and in transformation of mammalian cells, we monitored its activity by binding to a specific DNA probe in normal or transformed mouse NIH 3T3 cells. A 3- to 4-fold increase in the DNA-binding activity was found after serum stimulation of quiescent NIH 3T3 cells. A 2- to 3-fold activation was found after treatment with PMA or dibutyryl-cAMP, suggesting that different signal-transducing pathways could activate AP1 factor in these cells. PMA stimulation was dependent on new protein synthesis. In contrast to normal cells, a high serum-independent AP1 DNA-binding activity was found in NIH 3T3 cells transformed by simian virus 40. These results suggest that constitutive AP1 synthesis may be a crucial step in cellular transformation.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Activation of the polyomavirus enhancer by a murine activator protein 1 (AP1) homolog and two contiguous proteins.

The polyomavirus enhancer is composed of multiple DNA sequence elements serving as binding sites for proteins present in mouse nuclear extracts that activate transcription and DNA replication. We have identified three such proteins and their binding sites and correlate them with enhancer function. Mutation of nucleotide (nt) 5140 in the enhancer alters the binding site (TGACTAA, nt 5139-5145) for polyomavirus enhancer A binding protein 1 (PEA1), a murine homolog of the human transcription factor activator protein 1 (AP1). This mutation simultaneously reduces polyomavirus transcription and DNA replication. Reversion of this mutation simultaneously restores binding of PEA1 and both DNA replication and transcription. Binding of a second protein, PEA2, adjacent to the PEA1 site at nt 5147-5155 is enhanced by PEA1 binding, suggesting that these proteins interact. A third protein, PEA3, binds to the sequence AGGAAG (nt 5133-5138) adjacent to the PEA1 binding site; integrity of this late-proximal PEA3 binding site or an additional early-proximal site (nt 5228-5233) is important for enhancer function. We correlate binding of PEA1 and PEA2 with the induction of a DNase I-hypersensitive site in polyomavirus minichromosomes isolated from mouse fibroblasts.

Animals↗