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Biomedical subjects

J J Legros

Publications and source records attributed to J J Legros.

At least 73 records · Page 4Linked to original sources
PubMed1994

Pathogenic tracks in fatigue syndromes.

This review analyses the recent literature devoted to two related fatigue syndromes: chronic fatigue syndrome (CFS) and acute onset postviral fatigue syndrome (PVFS). The articles are grouped into five pathogenic tracks: infectious agents, immune system, skeletic muscle, hypothalamo-pituitary-adrenal (HPA) axis and psychiatric factors. Although a particular infectious agent is unlikely to be responsible for all CFS cases, evidence is shown that host-parasite relationships are modified in a large proportion of patients with chronic fatigue. Antibody titres against infectious agents are often elevated and replication of several viruses could be increased. Chronic activation of the immune system is also observed and could be due to the reactivation of persistent or latent infectious agents such as herpes viruses (i.e. HHV-6) or enteroviruses. It could also be favorised by an impaired negative feedback of the HPA axis on the immune system. A model is proposed where the abnormalities of the HPA axis are primary events and are mainly responsible for a chronic activation of the immune system which in turn induces an increased replication of several viruses under the control of cellular transcription factors. These replicating viruses together with cytokines such as TNF-alpha would secondarily induce functional disorders of muscle and several aspects of asthenia itself.

Enterovirus↗
PubMed1994

[The long progress of neurohypophyseal peptides].

Two neurohypophyseal peptides (vasopressin or antidiuretic hormone and oxytocin) belong to a family of peptides that are broadly widespread in the animal kingdom. These peptides are already found in unicellular species and differently distributed in hydra. Schematically, basic peptides related to vasopressin can be distinguished from neutral peptides related to oxytocin. Phylogenetic evolution of these two peptides shows that basic compounds are usually implicated in water metabolism regulation, but also through their central way of action, in important behaviour connected with survival of mankind (alertness, memorization, cardiovascular acceleration...) although neutral compounds are implicated in reproductive functions (carriage of spermatozoids in female genital tractus, expulsion phase of delivery, milk ejection reflex). Concerning behaviour, these compounds demonstrate properties favouring between subjects relationship (maternal behaviour settlement, including in birds, building of social links). Neuropsychiatric disturbances leading to an excess or a deficit of the central production of one of the groups of these neuropeptides could then be explained on basis of these general conclusions.

Animals↗
PubMed1993

Neurohypophyseal peptides and psychiatric diseases.

The study of neurohypophyseal function in various neuropsychiatric diseases is interesting because: (1) The main neurohypophyseal peptides vasopressin (AVP) and oxytocin (OT) share by themselves modulatory influence on behavior. (2) Hypothalamo-posterior pituitary axis is directly influenced by modifications of central neurotransmitter metabolism involved in behavior control.

Animals↗
PubMed1993

Oral contraceptives and the dexamethasone suppression test.

Among other confounding factors, the influence of the intake of estrogen-containing oral contraceptives on the dexamethasone suppression test (DST) results has never been specifically studied. Therefore, we performed 1 mg DSTs in 14 healthy women taking oral contraceptives and 14 age-matched women taking no oral contraceptives. Mean 0800h basal total cortisol was significantly higher among the women taking contraceptives than in the control group, whereas mean free cortisol did not significantly differ. At 1600h following DST, no significant difference existed between the two groups. Two subjects taking contraceptives and one control subject were considered DST nonsuppressors. These results confirm the powerful influence of oral contraceptives on basal total cortisol levels but suggest a lack of significant influence on DST results.

Adult↗
PubMed1993

Membrane translocation and relationship with MHC class I of a human thymic neurophysin-like protein.

Thymic epithelial and nurse cells (TEC/TNC) synthesize an oxytocin (OT)-like peptide in association with a neurophysin (NP)-related protein in a way similar to in the hypothalamo-neurohypophysial (NHP) system. The central T-cell tolerance of the NHP neuroendocrine functions have been proposed to be mediated through these thymic NHP-related peptides due to their close homology with the NHP neurohormones OT and vasopressin (VP). In order to investigate their putative presentation by proteins of the major histocompatibility complex (MHC), human thymic membranes were purified and passed through an immunoaffinity column using mAb B9.12 directed to the monomorphic determinant of human MHC class I proteins. This methodology provided the following observations: (1) a NP-like protein is translocated in human thymic membranes and is retained by B9.12 on the column; (2) the MW of this NP-like material (50-55 kD) is quite different from the MW of hypothalamic NP proteins (10 kD), and (3) this thymic NP-like protein could be identified on Western blots with mAb B9.12. The precise extent of this relationship between the thymic NP-like protein and the Ig/MHC superfamily is actually investigated through the characterization of the genetic mechanisms responsible for the thymic expression of NHP-related peptides. Given the physiological importance of OT and of its binding to NP for transport along the axonal processes of the NHP tract, we postulate that, somewhat analogously, the thymic NP-/MHC class I-related protein could be involved in the presentation of the OT-like peptide to immature T-cells.

Amino Acid Sequence↗
PubMed1992

Oxytocin blocks the environmentally conditioned compensatory response present after tolerance to ethanol-induced hypothermia in mice.

The present study tested the hypothesis that the attenuation by oxytocin of tolerance to ethanol-induced hypothermia relies upon an impairment of the putative conditioning processes underlying environment-specific tolerance. According to the conditioning model of tolerance, such tolerance occurs because an opposite compensatory response conditioned to ethanol-paired cues attenuates ethanol's effects. Tolerance to ethanol-induced hypothermia was established to a particular environment over 4 days by injecting mice (daily) with oxytocin 2 h before ethanol, outside the colony room. As controls, other mice were injected similarly but following testing in the animal room. We found that oxytocin suppressed the conditioned compensatory response, revealed by injecting saline to every group in the tolerance-associated environment. These results suggest that oxytocin acted, at least partly, via an inhibition of the associative learning processes that facilitate tolerance development.

Animals↗
PubMed1992

Apomorphine stimulation of vasopressin- and oxytocin-neurophysins. Evidence for increased oxytocinergic and decreased vasopressinergic function in schizophrenics.

Apomorphine challenge tests (0.5 mg SC) were performed in 14 normal male volunteers and in 9 male schizophrenic inpatients, drug-free for at least 2 wk. In the normal volunteers, apomorphine induced an increase of serum growth hormone (GH) (maximum at 40 min), of vasopressin-neurophysin (hNpI) (maximum at 20 min), and oxytocin-neurophysin (hNpII) (maximum at 20 min). The release of neurophysins was independent of digestive side effects. In the schizophrenics, the GH level and release pattern were similar to those in the controls. The basal level of hNpI was reduced (t0: 0.42 +/- 0.1 ng/ml in the schizophrenics and 0.66 +/- 0.05 ng/ml in the controls, p < 0.02). In contrast, the basal level of hNpII was increased (3.34 +/- 0.04 ng/ml in the schizophrenics to 0.92 +/- 0.21 ng/ml in the controls, p = 0.001). The response to apomorphine was blunted, with no significant release of hNpI or of hNpII. Although the hNpII data are consistent with an increased dopaminergic tone, the psychopathological meaning of the increased basal oxytocinergic and decreased vasopressinergic functions remains to be defined.

Adult↗
PubMed1992

Neurohypophyseal peptides and psychopathology.

The study of neurohypophyseal peptides in various neuropsychiatric disorders is of interest because the hypothalamo-posterior pituitary axis is directly influenced by modifications of central neurotransmitter metabolism involved in behaviour control. Moreover, the main neurohypophyseal peptides, namely vasopressin and oxytocin, are themselves capable of modifying behaviour. In this paper the author discusses current understanding of the anatomy and physiology of the main central vasopressinergic and oxytocinergic pathways, followed by a description of the principal actions of exogenously administered vasopressin and oxytocin on human behaviour. Finally, modification of endogenous neurohypophyseal function encountered in different pathological states are described.

Amino Acid Sequence↗
PubMed1991

Oxytocin attenuates tolerance not only to the hypothermic but also to the myorelaxant and akinesic effects of ethanol in mice.

Inhibition of ethanol tolerance by oxytocin has been demonstrated previously using the hypothermic effect only. The purpose of the present experiment was to investigate the effect of oxytocin on the development of tolerance to ethanol-induced hypothermia, myorelaxation and akinesia in mice. Four groups of mice received daily intraperitoneal injections of saline or oxytocin (0.005 mg) plus saline or ethanol (2 g/kg). The peptide was administered 2 hours before ethanol. For five consecutive days, temperature measurements were performed 20 minutes before and after ethanol injection. Myorelaxation and akinesia were evaluated following the second temperature measure. Oxytocin pretreatment, which had no intrinsic effects, resulted in a robust selective attenuation of tolerance to ethanol-induced hypothermia, myorelaxation and akinesia. These results suggest that the mechanisms for peptide modulation are common to these three typical effects of ethanol.

Animals↗
PubMed1991

Improvement in depressive illness is not associated with altered release of neurophysins over a course of ECT.

The hypothesis that the release of vasopressin-associated neurophysin (hNpI) or oxytocin-associated neurophysin (hNpII) is modified by a course of electroconvulsive therapy (ECT) was tested by the measurement of serum neurophysins before and after the first and last ECTs given to 17 unipolar depressed patients. Neither basal nor ECT-induced neurophysin release changed between the first and last ECTs. Data from the present study were combined with data from a previous published study to provide a sample of 29 unipolar depressed patients. In this extended sample, the release of hNpII after the first ECT was significantly correlated with improvement in symptoms of depression over a course of ECT as measured by the Hamilton Rating Scale for Depression and the Montgomery-Asberg Depression Rating Scale.

Adult↗
PubMed1991

Monoclonal antibodies to oxytocin: production and characterization.

To induce a good immune response to oxytocin (OT) we developed a two-step technique to conjugate OT to thyroglobulin (TG) using glutaraldehyde. We obtained 30 hybridomas recognizing OT-ovalbumin conjugates and 16 stable lines. Three monoclonal antibodies were selected for further characterization. One of them (O13) was found very specific for OT using three different techniques (enzyme-linked immunosorbent assay, radioimmunoassay and immunohistochemistry); it is directed to the C-terminal tripeptide. The other two probably recognize tyrosine containing epitope(s) also shared by vasopressin and other related nonapeptides.

Animals↗