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Biomedical subjects

B Legrand

Publications and source records attributed to B Legrand.

At least 19 recordsLinked to original sources
PubMed2002

Psychobiologic responses to 4 days of increased training and recovery in cyclists.

The psychobiologic status of cyclists after 4 days of training and the kinetics of recovery were assessed by measuring the sympatho-adrenal level, the central noradrenergic activity and the cortisol/testosterone status by non-invasive methods. For this purpose, urinary excretion of methoxyamines (metanephrine [MN], normetanephrine [NMN]), which are metabolites of circulating catecholamines, 3-methoxy-4-hydroxyphenyl glycol sulfate (MHPG-S), a metabolite of brain norepinephrine, and salivary output of cortisol and testosterone were measured in twelve national cyclists (aged 19.5 +/- 4.5 years), just before (T 1 ) and at the end of the training (T 2 ), and during the three following recovery days (R 1, R 2, R 3 ). Urinary and salivary samples were also collected during a period of relative rest, in order to get reference values (T 0 ). At T 0, T 1 and T 2, mood states, as measured by the Profile of Mood States, and rating of perceived muscle soreness were assessed. The overall mood and muscle soreness levels were not affected by the training. The load increased by 187 % as an average between the first and the fourth day of training. A significant increase in NMN levels and a decrease in T:F ratio were observed at T 2, while MHPG-S excretion remained unchanged. Persistent high urinary output of NMN and MN were observed during the post-training recovery period for 24 h (R 1 ) and 48 h (R 2 ), respectively. After 72 h of recovery (R 3 ), MN levels had returned to baseline while NMN output was lower than the control level. T:F values returned to their control levels within 48 h of recovery. The strenuous training seems to induce an alteration in peripheral neuro-endocrine parameters without modifications of central factors. The hormonal status remained altered for at least 1 day of post-training recovery and seemed to be achieved within 3 days.

Adaptation, Physiological↗
PubMed2001

Wetting and structural transition induced by segregation at grain boundaries: a monte carlo study.

Wetting of the Sigma = 5 (310) <001> symmetrical tilt grain boundary (GB) close to the solubility limit in the Cu(Ag) solid solution has been observed by means of Monte Carlo simulations at T = 600 K. More precisely, a finite thickness film almost pure in Ag, separating the two initial Cu(Ag) grains, can be obtained from a critical intergranular germ induced by the strong segregation of Ag in the GB. As this film is actually a single crystal, this implies a complete rearrangement of the GB core structure. Thus the initial GB is replaced by two Cu(Ag)/Ag(Cu) interfaces. Evidence is presented for the increase of the film thickness when approaching the solubility limit, as expected in wetting phenomena.

Journal Article↗
PubMed2000

Imaging the wave-function amplitudes in cleaved semiconductor quantum boxes

We have investigated the electronic structure of the conduction band states in InAs quantum boxes embedded in GaAs. Using cross-sectional scanning tunneling microscopy and spectroscopy, we report the direct observation of standing wave patterns in the boxes at room temperature. Electronic structure calculation of similar cleaved boxes allows the identification of the standing waves pattern as the probability density of the ground and first excited states. Their spatial distribution in the (001) plane is significantly affected by the strain relaxation due to the cleavage of the boxes.

Journal Article↗
PubMed1993

Evidence for a preferential V beta usage by the T cells which adoptively transfer diabetes in NOD mice.

Non-obese diabetic (NOD) mice become spontaneously diabetic as a result of a genetically programmed autoimmune process mediated by autoreactive T lymphocytes and directed against beta cell antigen(s). Studies dealing with T cell receptor (TcR) variable (V) gene usage by such autoreactive T lymphocytes have given contrasted results. Various reasons may explain these discrepancies: the multiplicity of antigenic epitopes putatively recognized by T cells, the ambiguity between specifically committed T cells and passenger lymphocytes homing randomly to the pancreas, the necessarily limited size of the T cell clone panels which have been analyzed for TcR rearrangements and, last but not least, the flexibility of T cell repertoires. To circumvent some of these difficulties, we have decided to concentrate upon the T cell population present in diseased animals and capable of transferring diabetes into young naive NOD recipients. This population, composed of CD4+ and CD8+ T cells, is presumably committed against the relevant beta cell antigens and is the most likely to reveal a bias in V gene usage if such a bias does indeed exist. To find out whether certain V beta genes are more frequently used than others by such pathogenic T cells, T lymphocytes from diabetic donors have been depleted in vitro of defined V beta subsets before being reinoculated into permissive recipients. Out of four V beta families probed under such conditions, three (V beta 8, V beta 5 and V beta 11) are neutral. Their absence neither increases nor reduces the final incidence of successful transfers, indicating that these gene segments are not preferentially used. In contrast, the depletion of V beta 6-positive T cells results in a severe reduction of transfers, suggesting that V beta 6 gene is used with a relatively high frequency by diabetogenic CD4+ and/or CD8+ T cells. To define more precisely which subset uses V beta 6 gene preferentially, we have performed mixing experiments with deleted and intact subsets. The results, based on disease transfer and insulitis severity, indicate that the V beta 6 bias affects predominantly the CD4+ subset. Thus, at variance with several studies concluding that V gene usage in NOD mice is heterogeneous, our present data suggest that disease transferring T cells use a relatively restricted set of V beta genes.

Animals↗
PubMed1993

Establishment of T-cell lines from infiltrated NOD islets by stimulation of specific T-cell receptor V beta segments.

The aims of this study were firstly to establish permanent T-cell lines from infiltrated NOD islets, by repeated stimulation of the antigen T-cell receptor with anti-V beta monoclonal antibodies (mAb) and, secondly, to characterize some of their cytotoxic and pathogenic properties. The use of anti-V beta antibodies was aimed at driving the expansion of the T cells in the absence of pancreatic antigen and, at the same time, at selecting lymphocytes expressing a given V beta gene product as an element of their TCR. Twelve lines were established as long-term cultures by regular stimulation with plastic-bound anti-V beta 6 or anti-V beta 8 mAb. The eight lines cultured with anti-V beta 6 mAb were phenotyped as early as one month after initiation and were all V beta 6+/V beta 8-. Three were CD8+ and five CD4+. Of the four lines established with anti-V beta 8 mAb, three were V beta 8+/V beta 6- and one (FD) was unexpectedly phenotyped as V beta 6+/V beta 8-. Clones derived from the FD line confirmed the expression of V beta 6. The cell-mediated cytolytic properties of the 12 lines were evaluated in two independent assays: an antibody-redirected assay to measure the lytic potential irrespective of antigen specificity and a direct cytolytic assay on YAC cells for assessing NK-like activity. The results indicate that practically all the lines (11 out of 12), irrespective of their CD4/CD8 phenotype or V beta expression, can exert cell-mediated cytotoxicity when their TCR/CD3 complex is linked to a target cell. On the other hand, anti-YAC activity is almost exclusively confined to CD8+ cell lines. Pathogenicity was evaluated in two CD4+ T cell lines, one which showed cytolytic activity in the redirected assay but not in the YAC assay (FD) and one which was totally devoid of cytotoxic activity (AH). The two lines were injected into newborn NOD mice with or without CD8+ polyclonal T cells. The results indicate that FD, the cytotoxic line, can induce severe lesions of insulitis when coinjected with polyclonal CD8+ T cells. In contrast, AH, the non-cytotoxic line, injected under the same conditions, induces no lesions. Altogether, the present data demonstrate the feasibility of establishing permanent T-cell lines on the basis of V beta expression.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Acquired allo-tolerance to major or minor histocompatibility antigens indifferently contributes to preventing diabetes development in non-obese diabetic (NOD) mice.

Diabetes in NOD mice represents the end stage of a genetically-programmed autoimmune process mediated by T lymphocytes and directed against insulin-producing beta cells. We have shown in a previous study that the course of the disease is significantly inhibited in NOD mice which have been made tolerant at birth to foreign histocompatibility antigens. This early T cell manipulation results in a significant delay of disease onset, reduced overall incidence and less severe alterations of islet cells. In order to characterize better the nature of the foreign tolerogenic determinants responsible for this protection, we have now examined separately the contribution of MHC and non-MHC antigens. Two lines of congenic mice were used as donors of tolerogenic cells, NOD.H-2b, which differ from NOD by the MHC-encoded antigens only, and B10.H-2g7, which differ by all the minor histocompatibility antigens encoded by the B10 background, but which share with NOD mice the same MHC haplotype. Our results show that NOD recipients of F1 semi-compatible cells become specifically tolerant to the set of alloantigens to which they were neonatally exposed. Unresponsiveness, assessed by lack of CTL generation, is profound and specific. Yet, despite the fact that distinct sets of alloreactive T cell precursors are silenced, mice made tolerant indifferently to major or minor histocompatibility antigens are significantly protected against overt diabetes. These results could mean that each set of MHC and non-MHC encoded determinants can independently cross-tolerize a sufficient proportion of the autoreactive repertoire to slow the natural course of the disease. Alternatively, neonatally-acquired tolerance might induce polyclonal activation of the immune system resulting in the suppression or the immunodeviation of potentially harmful, autoreactive T cell clones.

Animals↗
PubMed1981

The use of highly concentrated purified (by a large scale method) and long term liquid nitrogen stored foot-and-mouth disease viruses for the preparation of vaccines: physico-chemical quality controls and potency tests after storage.

In 1974 a new industrial technique for concentration and purification of FMD virus was presented at the OIE Conference. The bulk inactivated virus from this technique was stored in liquid nitrogen vapour until required for vaccine formulation. In 1981, having applied this technique regularly for seven years, we now describe the results obtained and the advantages gained in the field of trivalent O, A, C bovine vaccine production. Vaccines prepared from such bulk virus stocks after several years storage give good protection against virulent virus challenge.

Animals↗