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Biomedical subjects

J M Aubry

Publications and source records attributed to J M Aubry.

35 records · Page 2Linked to original sources
PubMed1996

Virucidal activity of pure singlet oxygen generated by thermolysis of a water-soluble naphthalene endoperoxide.

Using the water-soluble naphthalene carrier of singlet oxygen NDPO2, we have shown that pure singlet oxygen is able to inactivate enveloped viruses (human immunodeficiency virus type 1, herpes simplex virus type 1, cytomegalovirus, vesicular stomatitis virus), but has no effect on non-enveloped viruses (adenovirus and poliovirus 1). These results are related to the experiments on photoinactivation of viruses by hydrophobic photosensitizers (merocyanine 540, hypericin, phthalocyanines, hematoporphyrin and benzoporphyrin derivatives) and they strengthen the hypothesis that singlet oxygen plays a predominant role in this process.

Adenoviruses, Human↗
PubMed1996

Functional N-methyl-D-aspartate receptors in O-2A glial precursor cells: a critical role in regulating polysialic acid-neural cell adhesion molecule expression and cell migration.

The capacity for long-distance migration of the oligodendrocyte precursor cell, oligodendrocyte-type 2 astrocyte (O-2A), is essential for myelin formation. To study the molecular mechanisms that control this process, we used an in vitro migration assay that uses neurohypophysial explants. We provide evidence that O-2A cells in these preparations express functional N-methyl-D-aspartate (NMDA) receptors, most likely as homomeric complexes of the NR1 subunit. We show that NMDA evokes an increase in cytosolic Ca2+ that can be blocked by the NMDA receptor antagonist AP-5 and by Mg2+. Blocking the activity of these receptors dramatically diminished O-2A cell migration from explants. We also show that NMDA receptor activity is necessary for the expression by O-2A cells of the highly sialylated polysialic acid-neural cell adhesion molecule (PSA-NCAM) that is required for their migration. Thus, glutamate or glutamate receptor ligands may regulate O-2A cell migration by modulating expression of PSA-NCAM. These studies demonstrate how interactions between ionotropic receptors, intracellular signaling, and cell adhesion molecule expression influence cell surface properties, which in turn are critical determinants of cell migration.

Calcium↗
PubMed1995

Stress-induced changes in messenger RNA levels of N-methyl-D-aspartate and AMPA receptor subunits in selected regions of the rat hippocampus and hypothalamus.

The postsynaptic AMPA/kainate and N-methyl-D-aspartate-selective glutamate receptors are formed by several different subunits and the overall subunit composition of the receptor appears to determine its physiological and pharmacological properties. Although glutamatergic mechanisms have been implicated in various forms of hippocampal stress responses, the impact of stress on glutamate receptor subunit composition has not yet been elucidated. We have used cell-by-cell quantitative in situ hybridization to assess stress-induced changes in transcript levels of N-methyl-D-aspartate and AMPA receptor subunit genes in subdivisions of the rat hippocampus and hypothalamus that are implicated in the stress response. We found that 24 h after a single immobilization stress there was a significant increase in the cellular level of NR1 subunit messenger RNA (about 35-45% above control values) in hippocampal CA3 and CA1 pyramidal cells as well as in neurons of the hypothalamic supraoptic and paraventricular nuclei. Moreover, in the CA3 area we have detected a concomitant increase (50% above controls) in the level of NR2B subunit messenger RNA, while the expression of NR2A subunit gene did not change after stress. Stress induced a selective decrease in the level of AMPA receptor subunit glutamate receptor A messenger RNA in neurons of both the CA3 and CA1 areas (18 and 24%, respectively, below control values). These results suggest that the regulation of specific subunit messenger RNAs of the N-methyl-D-aspartate and AMPA receptors may be involved in altered hippocampal and hypothalamic responsiveness to glutamate and thus could play a critical role in stress-induced changes in their function.

Animals↗
PubMed1995

Adrenergic control of rat pineal NO synthase.

We have previously shown that exposure of rats to constant light (LL) induced a decrease in NO synthase (NOS) activity in the pineal gland. We present here the evidence that chronic (5 days) norepinephrine (NE) or isoproterenol treatment prevents the effect of LL and enhances pineal NOS activity in LL animals. This effect of NE appears to be mediated by beta-adrenoceptors, because it was not mimicked by the alpha-agonist phenylephrine. Pineal NOS activity was reduced in 16-h light/8-h dark animals treated for 4 days with the beta-adrenergic antagonist propranolol but not with the alpha 1-antagonist prazosin, indicating again an involvement of beta-adrenergic receptor in the control of NOS. Treatment with adrenergic antagonists did not affect cortical NOS activity, suggesting that the control of NOS is different in these two tissues or that the pineal expresses a specific isoform of the enzyme. Taken together, these data suggest that NE controls NOS in the pineal gland through beta-adrenergic receptors. To our knowledge, this represent the first demonstration of a regulation of NOS by a neurotransmitter in the CNS, as assayed under Vmax conditions.

Adrenergic Antagonists↗
PubMed1995

Corticotropin-releasing factor and vasopressin mRNA levels in roman high- and low-avoidance rats: response to open-field exposure.

Roman high- (RHA) and low- (RLA) avoidance rats are selected and bred for rapid versus non-acquisition of two-way, active avoidance behavior in a shuttle box. They also show a number of other behavioral differences which appear to be essentially related to emotional factors, the RLA rats being emotionally more sensitive. The ACTH secretory response to stressors is also augmented in RLA rats. We thus raised the question whether the expression of corticotropin-releasing factor (CRF) and vasopressin (VP), two neurohormones exerting a synergistic action on ACTH release from corticotropic cells, is different in the two strains. Steady-state mRNA levels were examined in the parvicellular neurons of the paraventricular nucleus under basal conditions and 4 h after a single 8-min exposure to an open-field stressor. In situ hybridization histochemistry with 35S-labeled oligonucleotide probes was followed by quantitative cell by cell autoradiography. When basal CRF and VP mRNA levels were compared in the two lines, we found that the RLA rats had a significantly higher VP-labeling density than the RHA rats. No difference was found for CRF mRNA. During open-field exposure, we observed behavioral differences paralleled by elevated corticosterone compatible with an increased emotional response in RLA rats. Open-field exposure produced a significant increase in CRF but not VP mRNA in both RHA and RLA rats (by 43 and 57%, respectively). These results suggest that differences in basal VP expression in CRF neurons may participate in the mechanisms underlying the hyperactivity of the hypothalamo-pituitary-adrenal (HPA) axis in the emotionally more sensitive RLA rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1995

Isolation from bovine haemoglobin of a peptide that might be used as a potential hydrophobic photosensitizer carrier.

The isolation of a peptic hydrolysate and of a pure peptide from bovine haemoglobin is described. These peptides were used to solubilize an insoluble photosensitizer in order to study their utilization as a carrier for photochemotherapy. Protoporphyrin IX was used as a model of an insoluble photosensitizer. Solubilization of protoporphyrin IX was first performed with the total haemoglobin hydrolysate, then with peptide fractions, and finally with a pure peptide isolated from this fraction by reversed-phase HPLC. The molecular mass and the primary structure of the pure peptide were determined by fast-atom-bombardment and tandem MS (molecular mass 1648 Da). The singlet oxygen quantum yield of the protoporphyrin IX-peptide complex was determined.

Amino Acid Sequence↗
PubMed1994

NK1 receptor expression by cholinergic interneurones in human striatum.

Neurokinin-1 (NK1) receptor expression in human striatum was analysed using the polymerase chain reaction. To determine whether cholinergic interneurones express this receptor, in situ hybridization histochemistry was then applied to caudate nucleus and putamen. Radioactive oligonucleotide probes specific for choline acetyltransferase (ChAT) and NK1 receptor mRNA were used on adjacent cryostat sections. All of the 160 identified neurones positive for ChAT were also labelled for NK1 receptor. Moreover, in the caudate nucleus, NK1 receptor mRNA was detected in a population of large neurones that were not cholinergic. These results are consistent with the hypothesis that NK1 receptor-mediated mechanisms are involved in the function of cholinergic interneurones. This might be relevant to pharmacological or pathophysiological situations where substance P inputs are modified.

Aged↗
PubMed1994

Stressor-specific increase of vasopressin mRNA in paraventricular hypophysiotrophic neurons.

Cellular levels of vasopressin (VP) and corticotropin-releasing factor (CRF) RNA transcripts were determined in hypophysiotrophic neurons after open-field and immobilization stress using quantitative in situ hybridization. We found that 8 min open-field stress is sufficient to produce a significant up-regulation of CRF mRNA, without any concomitant changes in the level of VP mRNA. In contrast, 8 min immobilization stress resulted in an increased labeling density of both CRF and VP mRNAs. These results suggest that the level of CRF and VP transcripts in parvicellular hypophysiotrophic neurons is differentially regulated in a stressor-specific manner.

Animals↗
PubMed1994

Photophysical and photobiological activities of a porphyrin peptide fraction derived from haemoglobin.

In a previous study, we described the preparation of a porphyrin peptide hydrolysate from haemoglobin, its isolation and its analysis by high performance liquid chromatography (HPLC) and fast atom bombardment (FAB) mass spectrometry. The purpose of the present paper is to test the photosensitizing activity of this fraction. We determined the singlet oxygen quantum yield (phi delta) in order to quantify the efficiency of the porphyrin peptide fraction. The quantum yield is about phi(1O2)=0.06. An analysis of the phototoxic effect on tumour cells in culture was performed and compared with haematoporphyrin derivative (HpD), the only photosensitizer in clinical use at present. The phototoxicity of the porphyrin peptide fraction is weaker than that of HpD. However, for a porphyrin dose of 50 micrograms ml-1, the difference in phototoxicity is low, and in the absence of irradiation porphyrin peptides are less toxic than HpD. These results suggest that porphyrin peptides could be potent photosensitizers; moreover, they are of great interest since they allow the solubilization of hydrophobic porphyrins and could be applied in the future as insoluble photosensitizer carriers.

Cell Line↗
PubMed1993

Coexpression of dopamine D2 and substance P (neurokinin-1) receptor messenger RNAs by a subpopulation of cholinergic neurons in the rat striatum.

Amongst different intrinsic and extrinsic inputs, cholinergic striatal interneurons receive afferents from the dopaminergic nigrostriatal projection and from local collaterals of striatonigral cells containing substance P. The following study demonstrates that both dopamine D2 and substance P (neurokinin-1) receptors are expressed by a large proportion of cholinergic interneurons. Using in situ hybridization on triplet adjacent sections with radioactive probes specific for choline acetyltransferase, substance P receptor, and D2 receptor long-splicing form messenger RNAs, we show that these interneurons can be divided into four subpopulations in terms of substance P and D2 receptor expression. A majority of these neurons coexpress both receptors (76%), while other minor subpopulations express either one (respectively, 16% and 2%) or none of them (6%). Our results also show that substance P receptor is expressed by striatal neurons that are not cholinergic. These findings are in agreement with the concept that striatal cholinergic interneurons are heterogeneous in terms of input-output connections and the type of receptors expressed. Moreover, the presence of substance P and D2 receptors on a majority of these neurons is relevant to a putative role of cholinergic interneurons in several conditions such as various neurodegenerative disorders or antipsychotic drug administration, where substance P and dopamine inputs are modified.

Animals↗
PubMed1993

Up-regulation of vasopressin mRNA in paraventricular hypophysiotrophic neurons after acute immobilization stress.

Cellular levels of vasopressin (VP) and corticotropin-releasing factor (CRF) mRNAs were determined in the rat hypothalamic paraventricular nucleus after acute immobilization stress. Messenger RNA levels were measured by in situ hybridization histochemistry using 35S-labeled synthetic DNA oligonucleotide probes and quantitative autoradiography. Analysis of histograms related to density values revealed that two hours after immobilization the average cellular VP and CRF mRNA levels were significantly increased (145 +/- 30.3 and 68 +/- 21.3%, respectively, above control values). Moreover, the number of VP-expressing parvicellular neurons was doubled in stressed rats relative to controls. These results indicate that single acute immobilization stress is sufficient to up-regulate VP as well as CRF mRNA production in the hypothalamic CRF-neurosecretory system.

Animals↗
PubMed1993

Stress-induced increase in vasopressin and corticotropin-releasing factor expression in hypophysiotrophic paraventricular neurons.

The concerted action of CRF and vasopressin (VP) plays a critical role in regulating ACTH release from anterior pituitary cells. In this study, we have explored the expression of these neurohormones in hypophysiotropic paraventricular neurons after repeated exposure of rats to immobilization stress. Cell by cell quantitative in situ hybridization was used to evaluate the steady state level of mRNAs coding for VP and CRF. We found that 16 daily stress exposures resulted in a significant increase in the average cellular level of CRF and VP mRNAs (150% and 200% of control levels, respectively). Moreover, in the repeatedly stressed group, the number of VP-expressing parvicellular neurons was approximately doubled relative to the control value. Using quantitative immunoelectron microscopy, VP- and CRF-immunoreactive sites were assessed in the dense core vesicle compartment of CRF axon terminals in the external zone of the median eminence. We found that after repeated stress, the immunolabeling of VP was augmented, while that of CRF was slightly decreased. Concurrently, we observed a significant increase in the proportion of CRF nerve terminals that were VP positive (from 50% in controls to 90% in stressed animals). We conclude that the observed changes in CRF neurons may represent a physiological response to increased functional demand and may lead to alterations in the composition of the ACTH-releasing signal.

Animals↗
PubMed1993

Singlet oxygen-induced DNA damage: product analysis, studies of biological consequences and characterization of mutations.

The DNA lesions induced by free 1O2 and the biological and mutagenic consequences of 1O2-induced DNA damage have been studied. Using anion exchange HPLC, reverse-phase HPLC with electrochemical detection and 32P-postlabelling methods, we have shown that 1O2 reacts with 2'-deoxyguanine 3'-monophosphate (dGp) but not with any other dNp. Reaction with dGp yields a large number of products; one minor product was identified as 7-hydro-8-oxo-2'-deoxyguanosine 3'-monophosphate (8-oxo-dGp), and a second tentatively as a formamidopyridine derivative of dGp. 8-Oxo-dGp was also found after reaction of 1O2 with single-stranded (ss) DNA, double-stranded (ds) DNA or an oligonucleotide (16-mer) having one G. With the oligonucleotide we found a second unidentified reaction product. With ss DNA, 8-oxo-dG was a much more prominent product than in the reaction of 1O2 with free dGp and the yield was about eight-fold higher than with ds DNA. This agrees with our finding that ss M13 DNA is at least 100-fold more sensitive than ds M13 DNA to biological inactivation by 1O2. The inactivation of ss M13 DNA must be largely due to 1O2-induced lesions other than 8-oxo-dG. In agreement with the observed preferential reaction of 1O2 with dG, most of the mutations induced by 1O2 in ss or ds M13mp10 DNA occurred at a G or G/C basepair, respectively. A preference for G(C) to T(A) transversions was observed for which 8-oxo-dG might have been responsible. In ss DNA, a significant number of mutations are characterized by the fact that a G is deleted.

Bacteriophage M13↗
PubMed1992

Interaction of singlet oxygen with DNA and biological consequences.

To study the interaction of singlet oxygen (1O2) with DNA and the biological consequences of 1O2-induced DNA damage, we used the thermodissociable endoperoxide of 3,3'-(1,4 naphthalidene) dipropionate (NDPO2) as a generator of free 1O2 in reactions with (1) 2'-deoxynucleoside 3'-monophosphates (dNps), (2) an oligonucleotide (16-mer) having one deoxyguanine (dG), (3) native and denaturated rat kidney DNA and (4) single-stranded (ss) and double-stranded (ds) bacteriophage M13mp10 DNA. Using both anion exchange and reversed phase HPLC and 32P-postlabeling analyses, it was found that exposure of the various dNps to chemically generated 1O2 led to a detectable reaction with dGp and not with dAp, dCp, d5mCp or Tp. The reaction with dGp led to degradation of this nucleotide and the formation of a large number of reaction products, one of which could be identified as 7-hydro-8-oxo-2'-deoxyguanosine 3'-monophosphate (8-oxo-dGp). A second product could tentatively be identified as a formamido pyrimidine derivative of dGp (Fapy-dGp). When ss DNA, ds DNA or the oligonucleotide were exposed to 1O2, the formation of 8-oxo-dG could also be demonstrated. With the oligonucleotide, we found a so far unidentified reaction product. Under the same reaction conditions the yield of 8-oxo-dG was about 8-fold higher in ss DNA than in ds DNA. In ss DNA 8-oxo-dG seemed to be a more prominent product than in the case of reaction of 1O2 with free dGp. Reaction of 1O2 with ss or ds M13mp10 DNA led to biological inactivation of these DNAs, ss DNA being at least 100-fold more sensitive than ds DNA. It could be concluded that inactivation of the ss DNA must be largely due to 1O2-induced DNA lesions other than 8-oxo-dG. In agreement with the observed preferential reaction of 1O2 with dG most of the so far sequenced mutations, induced by 1O2 in a 144 bp mutation target sequence inserted in the lacZ alpha gene of ss or ds M13mp10 DNA, occurred at a G or G/C base pair respectively. A preference for G(C) to T(A) transversions can be observed for which 8-oxo-dG might have been responsible. In ss DNA a significant number of the mutations are characterized by the fact that a G is deleted.

Animals↗
PubMed1987

DNA damage by chemically generated singlet oxygen.

A naphthalenic endoperoxide was used as a non-photochemical source of singlet oxygen (1O2) to examine some interactions between this reactive oxygen species and DNA. High molecular weight DNA (ca. 10(8) daltons) was exposed to 120 mol m-3 1O2 (cumulative concentration) and analyzed for interstrand crosslinkage by hydroxyl apatite chromatography following formamide denaturation. No evidence for 1O2-induced interstrand crosslinking was obtained. The capacity of 1O2 to generate strand breaks in single-stranded (ss) and double-stranded (ds) DNA was investigated by sucrose gradient centrifugation analysis of bacteriophage phi X174 DNA. No direct strand breaks could be detected at neutral pH, whereas extensive strand breakage was observed after treatment with alkali. Possible biological consequences of 1O2-exposure were assessed by examining the plaque-forming capacity of ss and ds phi X174 DNA molecules using wildtype Escherichia coli spheroplasts as recipients. Without any further treatment with heat or alkali, exposure to the endoperoxide resulted in a time- and dose-dependent inactivation, ss DNA being considerably more sensitive than ds DNA. From the present results and those reported earlier (Nieuwint et al.,) we infer that 1O2-induced inactivation of phi X174 DNA is not due to DNA backbone breakage nor to interstrand crosslinking, but rather to some form of damage to the base or sugar moiety of the DNA, the exact nature of which remains to be elucidated.

Bacteriophage phi X 174↗
PubMed1985

Inability of chemically generated singlet oxygen to break the DNA backbone.

The capacity of a photodynamic and a chemical source of singlet molecular oxygen to cause DNA strand breakage at pH 7.8 was compared in the following systems: (1) dissolved rose bengal plus light (400-660 nm), (2) a novel water-soluble naphthalene-derived endoperoxide showing temperature-dependent singlet oxygen release, in the absence of light. Covalently closed circular DNA was efficiently converted to the open (relaxed) form upon exposure to dissolved rose bengal plus light in a time-dependent reaction, showing that this system was capable of causing DNA strand breakage at pH 7.8. The reaction was greatly reduced under hypoxic conditions (less than 5 p.p.m. O2), was stimulated when using D2O instead of H2O as a solvent and was not inhibitable by superoxide dismutase, indicating that singlet oxygen was a critical intermediate. However, comparatively large fluxes of singlet oxygen generated by the endoperoxide completely failed to produce DNA strand breaks. We conclude that, although singlet oxygen seems to play a role in DNA strand breakage by rose bengal plus light, singlet oxygen per se is very inefficient if not completely incapable of causing DNA strand breakage.

DNA Damage↗