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Biomedical subjects

V Lemaire

Publications and source records attributed to V Lemaire.

At least 37 records · Page 2Linked to original sources
PubMed2000

Prenatal stress produces learning deficits associated with an inhibition of neurogenesis in the hippocampus.

Early experiences such as prenatal stress significantly influence the development of the brain and the organization of behavior. In particular, prenatal stress impairs memory processes but the mechanism for this effect is not known. Hippocampal granule neurons are generated throughout life and are involved in hippocampal-dependent learning. Here, we report that prenatal stress in rats induced lifespan reduction of neurogenesis in the dentate gyrus and produced impairment in hippocampal-related spatial tasks. Prenatal stress blocked the increase of learning-induced neurogenesis. These data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for psychopathological vulnerabilities in aging.

Animals↗
PubMed2000

[Joint manifestations related to Clostridium difficile].

BACKGROUND: Reactional joint disease subsequent to digestive tract infections have been well studied for Salmonella, Shigella, Yersinia and Campylobacter. Association with HLA B27 is well documented. A review of the literature since 1976 disclosed 23 cases of articular and extra-articular inflammatory reactions following pseudomembranous Clostridium difficile infection. CASE REPORT: We describe 2 new cases which followed a favorable course. This is the usual outcome although inflammatory manifestations may persist or relapse. DISCUSSION: The pathophysiological interest of this condition lies in the pathogenic potential of Clostridium difficile which appears to be directly related to toxin production. This would suggest an immune mechanism rather than pure infection.

Adult↗
PubMed2000

Specific expression of matrix metalloproteinases 1, 3, 9 and 13 associated with invasiveness of breast cancer cells in vitro.

Several matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) were studied in highly invasive (MDA-MB-231) and slightly invasive (MCF-7, T47D, BT-20) breast cancer cell lines. Investigations were carried out at the protein level and/or at the mRNA level, either in cells cultured as monolayers on plastic, or in cells seeded on a thin layer of Matrigel basement membrane matrix. Analysis of MMP expression by RT-PCR showed expression of MMP-1. MMP-3, and MMP-13 in highly invasive MDA-MB-231 cells, but not in slightly invasive cell lines. The extracellular secretion of MMP-1 and MMP-3 by MDA-MB 231 cells could be also shown by ELISA. TIMP-1 and TIMP-2 mRNAs were found in all cell lines, however, the extracellular secretion of both TIMPs was much higher in MDA-MB-231 cells than in the other cell lines. When the cells were cultured on Matrigel matrix, MMP-9 expression was induced in MDA-MB-231 cells only, as assessed by RT-PCR and zymography experiments. The invasive potential of MDA-MB-231 cells evaluated in vitro through Matrigel was significantly inhibited by the MMP inhibitor BB-2516, by 25% and 50% at the concentrations of 2 x 10(-6) M and 10(-5) M, respectively. In conclusion, our data show that highly invasive MDA-MB-231 cells but not slightly invasive T47D, MCF-7 and BT-20 cells express MMP-1, MMP-3, MMP-9 and MMP-13. MMP-9 which is specifically up-regulated by cell contact to Matrigel, may play a key role in the invasiveness of MDA-MB-231 cells through basement membranes.

Base Sequence↗
PubMed2000

Deletion of the 5'-ABL region: a recurrent anomaly detected by fluorescence in situ hybridization in about 10% of Philadelphia-positive chronic myeloid leukaemia patients.

Inclusion of the BCR-ABL ES probe in routine cytogenetics led to the identification of a subgroup of Philadelphia positive (Ph+) chronic myeloid leukaemia patients characterized by a 5'-ABL deletion. This anomaly was observed in 5/51 cases (9.8%). Cytological and clinical data suggest that the 5'-ABL deletion may be associated with dysplastic features of polymorphonuclear cells and metamyelocytes and a short chronic phase duration.

Adult↗
PubMed1999

Behavioural trait of reactivity to novelty is related to hippocampal neurogenesis.

The hippocampal formation is one of the brain areas where neurogenesis persists during adulthood, with new neurons being continuously added to the population of dentate granule cells. However, the functional implications of this neurogenesis are unknown. On the other hand, the hippocampal formation is particularly concerned with the detection of novelty, and there are indications that dentate granule cells play a significant role in this function. Recently, the existence of inter-individual differences in behavioural reactivity to novelty has been evidenced, related to differences in the reactivity of the hypothalamic-pituitary-adrenal axis (HPA). Rats that are highly reactive to novelty (HR) exhibit a prolonged corticosterone secretion in response to novelty and to stress when compared with low reactive rats (LR). Taking advantage of the existence of these inter-individual differences, we investigated whether neurogenesis in the dentate gyrus is correlated with the behavioural trait of reactivity to novelty. Rats were first selected according to their locomotor reactivity to a novel environment. Two weeks later, cell proliferation, evaluated by the incorporation of 5-bromo-2'-deoxyuridine (BrdU) in progenitors, was studied by immunohistochemistry. We found that cell proliferation in the dentate gyrus was negatively correlated with locomotor reactivity to novelty. Indeed, cell proliferation in LR rats was twice that observed in HR rats. In contrast, survival of nascent neurons was not influenced by the behavioural trait of reactivity to novelty. Using an unbiased stereology, we show that LR rats had more cells within the granule cell layer of the dentate gyrus than did HR rats. These results demonstrate the existence of inter-individual differences in neurogenesis and total granule cell number within the dentate gyrus. These differences in hippocampal plasticity can be predicted by the behavioural trait of reactivity to novelty.

Animals↗
PubMed1998

Comparison of the neuroendocrine responses to stress in outbred, inbred and F1 hybrid rats.

In order to study the genetic factors involved in the neuroendocrine responses to stress, we have compared the intensity of the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system activation following a 60 minute-restraint stress or after a 10 minute-exposure to a novel environment in three rat strains : outbred Wistar, inbred Brown Norway and Fischer 344, and F1 hybrid Brown Norway x Fischer 344 rats. The basal activity of the HPA axis did not differ between the four groups of rats whereas Brown Norway rats had the lowest release of corticosterone following restraint stress. Although differences in plasma adrenocorticotropic hormone failed to reach significance after exposure to a novel environment, the lowest level of corticosterone was found in Brown Norway rats. This lower release of corticosterone in Brown Norway rats has probably an adrenal origin as suggested by the ratios of corticosterone to ACTH levels following exposure to a novel environment: 632 +/- 222, 200 +/- 45, 636 +/- 89, 258 +/- 65 in Wistar, Brown Norway, Fischer 344 and F1 hybrids, respectively. This trait was dominant over the "adrenal responsive" phenotype of the Fischer 344 rat strain. In response to novelty, the lowest levels of prolactin and renin activity were found in plasma of Brown Norway and Wistar rats and the highest in Fischer 344 and F1 hybrid Brown Norway x Fischer 344 rats, the "high response" phenotype of the Fischer 344 strain being dominant. No strain-related difference was found in plasma glucose and either adrenal tyrosine hydroxylase or phenylethanolamine N-methyl transferase activity. Taken together, these data suggest that 1) genetic factors might contribute to the interindividual differences in neuroendocrine responses to stress and 2) subsets of these responses are controlled by specific genetic factors.

Adrenal Glands↗
PubMed1997

Adrenal axis activation by chronic social stress fails to inhibit gonadal function in male rats.

Stress in males via the hypothalamic-pituitary-adrenal (HPA) axis may set into motion varied physiological alterations, including dysfunction of the hypothalamic-pituitary-gonadal (HPG) axis. However, the influence of the HPA on the HPG axis may not always be inhibitory. Presence or absence of stimuli of sexual significance that typically activates the HPG axis may alter the influence of the adrenal axis on gonadal axes. In this project, we used male rats and chronic social stimulation that included brief or extended periods with female rats to examine HPA-HPG axes interactions. In experiment 1, we used intact males and a 'chronic social stress' paradigm developed in our previous research that induces social instability by daily changing the membership of group-housed males with females. Thymus weight was reduced and corticosterone levels were marginally increased by chronic social stress, indicating a HPA axis hyperactivity. The HPG axis was also activated as shown by the increased weight of the androgen-sensitive sex structures. These results indicate that when these two axes are stimulated together, neither interferes with nor suppresses activities of the other. Implants of corticosterone pellets to adrenalectomized animals that maintained constant, high corticosterone levels failed to reverse the gonadal hyperactivity induced by sexual stimulation. In a second experiment, we studied the influence of different intensity of sexual stimulations on HPA-HPG axes interactions. Increased corticosterone levels and adrenal weight, indicating a HPA hyperactivity, failed to inhibit HPG hyperactivity as measured by the increased sexual organs weight, whatever the sexual intensity of the stimulation. This work demonstrates that the gonadal axis is freed from suppression when sexual stimulation occurs together with stress. The general conclusion is that the nature of complex social settings is important in determining interactions between the two neuroendocrine axes.

Adrenal Glands↗
PubMed1997

Social motivation in recently weaned rats is modified by opiates.

An open field choice test was used to determine whether maternal deprivation enhanced the motivation to stay close to the mother. Pups could choose between the dam, 3 sisters and 3 unknown animals of the same age. In addition, an empty enclosure identical to those that contained the stimulus animals were present as a nonsocial choice. Rats that were separated from their mother at 20 days of age and tested about 13 h later were compared to animals that had stayed with the mother until just before the test. It was found that maternal separation increased the time spent close to the mother and reduced that spent close to strangers or an empty enclosure. In fact, weaned animals spent far more time close to the mother than they spent close to any other available choice. Moreover, the mean duration of visits to the mother was much increased during the latter half of the 60-min test. These data were interpreted as showing that the mother had rewarding properties, and that maternal deprivation increased her reward value. In further experiments, the role of opioids for this increase in reward value was evaluated. Morphine enhanced the time spent close to the mother, but only in animals that had been subjected to maternal deprivation for about 13 h. Naloxone had the opposite effect. These data show that the mother's reward value is altered when the activity of opioid systems is modified. It is suggested that the mother acquires rewarding properties because of association with nutritive suckling-induced opioid release.

Analysis of Variance↗
PubMed1995

Telemetered recording of blood pressure and heart rate in different strains of rats during chronic social stress.

The role of stress in the etiology of high blood pressure and the biological mechanisms involved are still not clear. We have recently developed a paradigm of chronic social stress based on social instability and cohabitation with females, in which the different neuroendocrine responses to stress can be independently triggered. In this work, we used a telemetry technique to record blood pressure and heart rate chronically in freely moving undisturbed rats to study the influence of chronic social stress on blood pressure and heart rate in normotensive rats (Wistar and Long-Evans) and in Borderline Hypertensive Rats (BHR). No increase of blood pressure could be seen for one month of social stress in either strain. Wistar and Long-Evans rats were fully sensitive to social pressure, as shown by the changes in body weight, but may lack a specific vulnerability of the cardiovascular system. Conversely, Borderline Hypertensive rats have the genetic predisposition to develop hypertension but do not appear to be sensitive to social stimulations in the present experimental conditions. The experimental protocol used here should allow further investigation of the various possible sources of failure to induce chronic cardiovascular changes by social stress, such as blood pressure measurement techniques, social stress protocols, and genetic aspects of psychobiological and cardiovascular vulnerability to stress.

Animals↗
PubMed1994

Chronic social stress conditions differentially modify vulnerability to amphetamine self-administration.

Using social instability and cohabitation with females as chronic stress, we observed that neuroendocrine systems were differentially activated according to the experimental design. We show here that amphetamine self-administration, a paradigm to study the reinforcing effects of psychostimulants, is also differentially affected by these conditions. Coexistence with females increases amphetamine self-administration and this effect is reduced when social instability is superimposed. On the other hand, locomotor response to amphetamine is not modified by either social factor, suggesting a specific involvement of a subset of dopaminergic neurons.

Amphetamine↗
PubMed1994

[Bone metastases in epidural invasion of gastrinoma].

Malignant gastrinoma is a nonbeta islet cell tumor which rarely disseminates to the bone. However, in the case reported herein, diffuse metastatic bone disease with symptomatic epidural spread developed. Somatostatin and 99mTc-HDP bone scans demonstrated hot spots in the same sites, establishing that the bone lesions contained somatostatin receptor. Irradiation was effective in relieving pain.

Adult↗
PubMed1993

Regulation of catecholamine-synthesizing enzymes in adrenals of Wistar rats under chronic stress.

We have shown previously that chronic social stress has differential effects on adrenal weight and on tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) specific activity, depending on the experimental design. To determine the role of the sympathetic nervous system and of the hypothalamo-pituitary-adrenocortical axis (HPAA) in these modifications, we studied the mechanisms of regulation of these parameters in basal conditions as well as in response to reserpine treatment and chronic social stress in the Wistar strain of rats. We found that the adrenal weight is mostly dependent on the activity of the HPAA, which is increased in male rats living in mixed-sex colonies. PNMT specific activity is regulated by splanchnic innervation, confirming that its induction by social instability is a consequence of sympathetic nervous system hyperactivity. The increase of TH specific activity, as seen in unstable, mixed-sex colonies, is not under sympathetic control. However, we show that the pituitary may exert a tonic inhibitory influence, dependent on the sympathetic innervation. These data confirm that the HPAA and the sympathetic nervous system may be independently triggered in chronic social stress conditions.

Adrenal Glands↗
PubMed1993

Psychosocial stress can induce chronic hypertension in normotensive strains of rats.

We report on five 6-month experiments during which five colonies of four male and four female rats were exposed to psychosocial stress. Monthly blood pressure measurements by a tail-cuff method showed a modest (10 mm Hg) increase in two studies using Sprague-Dawley rats. In two further studies using the more aggressive Long-Evans strain, terminal direct carotid arterial pressures were taken as well, and in one study the differences exceeded 20 mm Hg. A fifth study used the Wistar-Kyoto, hyperactive (WKHA) strain developed by Hendley, and no differences were observed. Heart and adrenal weights; adrenal catecholamine synthetic enzymes; and heart, aortic, and kidney histology were measured and showed significant changes, which for the most part paralleled blood pressure changes. Social instability and the associated blood pressure changes were made more severe by periodic mixing of males from different colonies. This had no effect on the peaceable WKHA rats, some effect on the Sprague-Dawley rats, and a severe effect on the Long-Evans rats. The WKHA rats failed to show blood pressure changes despite stress-induced increases in heart and adrenal weights. Thus, different types of psychosocial stress and different genetics combine to induce a variety of neuroendocrine changes, not all of which necessarily lead to increased blood pressure.

Adrenal Glands↗
PubMed1992

Prolonged increase of corticosterone secretion by chronic social stress does not necessarily impair immune functions.

The influence of a chronic social stress upon immunity was investigated in Wistar rats, submitted for four weeks to two different behavioral situations, balanced in a factorial design: housing with three females and membership rotation. The combination of these two factor led to adrenal enlargement (43.3%), thymus involution (39.5%) and increased basal corticosterone levels, all indices of activation of the hypothalamic-hypophysis-adrenal axis. However, neither natural killer cell activity, splenocyte reactivity to mitogen nor the rate of spontaneous development of antibodies against Mycoplasma pulmonis, a common pathogen of the respiratory tract, were changed in the endocrine activated animals. Analysis of the data on kinetics of stress at 1, 7 and 28 days after the initial mixing of the animals gave the same results. These data question the immunosuppressant activity usually conferred to corticosteroids, at least when adrenal hyperactivity is induced by chronic environmental stressors.

Adrenal Glands↗
PubMed1991

Life events-induced decrease of corticosteroid type I receptors is associated with reduced corticosterone feedback and enhanced vulnerability to amphetamine self-administration.

In this study, we attempted to find out whether a social stress-induced increase in the vulnerability to acquire amphetamine self-administration was associated with a change in number of hippocampal corticosteroid receptors. This was examined in two types of sex-mixed colonies of rats. Animals were maintained for 4 weeks in: (1) 'stable social condition', membership did not change after constitution of the colony; (2) 'unstable social condition', the males were changed daily in a random design. The animals living in the 'stable social' conditions had: (1) a lower number of hippocampal type I corticosteroid receptors; (2) a longer duration of the increase in plasma corticosterone after exposure to novelty; (3) a higher vulnerability to acquire amphetamine self-administration. These findings suggest that a decrease in hippocampal type I corticosteroid receptors may be one of the biological mechanisms responsible for the impaired corticosterone feedback control observed in vulnerable animals. These findings throw more light on the role of hypothalamo-pituitary-adrenal axis in the modulation of adaptive behavior. The availability of drugs which are specific for corticosteroid receptors could represent a new approach to the therapy of certain behavioral disturbances.

Adrenalectomy↗
PubMed1991

[Vasculitis and neoplasms. 14 cases].

Fourteen cases of vasculitis associated with a neoplasm are reported. The vasculitides were classified as: leukocytolytic vasculitis 7, periarteritis nodosa 4, purpura rheumatica 1, cutaneous granulomatous vasculitis 1, microvasculitis nervosa 1. The neoplasms were diagnosed as: 10 hemopathies (including 4 cases of refractory anemia) and 5 solid tumors (1 patient had 2 tumors). The cutaneous manifestations (purpura, papules, subcutaneous nodules, etc.) and fever were the most common, while joint and neurological involvement were the rarest. The evolution of the vasculitis was usually corticosensitive and independent of the underlying neoplasm. A review of the literature revealed that these vasculitides (primarily leukocytolytic) were frequently associated with dysplastic myelogenous syndromes and hairy cell leukemia, while bronchopulmonary and colonic neoplasms were the most common solid tumors. The mechanisms giving rise to these vasculitides are discussed.

Aged↗