Les bulles « robustes »:Pourquoi il faut construire des logements en région parisienne

« Bulle » ou « pas bulle » ? La question taraude les observateurs et les acteurs du marché immobilier français. Nous examinons dans cet article les éléments empiriques et théoriques qui expliquent la hausse des prix récente et sa résistance aux retournements conjoncturels. En combinant la notion de bulle économique, les arguments de l’économie spatiale et une analyse d’économie politique, nous suggérons que la valorisation importante de l’immobilier en France est le résultat d’une logique rationnelle et conforte les intérêts des acteurs locaux. Dès lors, la forte valorisation peut être considérée comme une « bulle robuste », à même de résister à des chocs importants. Cette bulle organise un transfert intergénérationnel et peut avoir des effets positifs. Elle peut également renforcer la ségrégation spatiale, alimenter les inégalités territoriales et empêcher d’exploiter les économies d’agglomération possibles. L’analyse est détaillée sur la région Ile-de-France où ces phénomènes sont particulièrement marqués

Matrix Rigidity Induces Osteolytic Gene Expression of Metastatic Breast Cancer Cells

Nearly 70% of breast cancer patients with advanced disease will develop bone metastases. Once established in bone, tumor cells produce factors that cause changes in normal bone remodeling, such as parathyroid hormone-related protein (PTHrP). While enhanced expression of PTHrP is known to stimulate osteoclasts to resorb bone, the environmental factors driving tumor cells to express PTHrP in the early stages of development of metastatic bone disease are unknown. In this study, we have shown that tumor cells known to metastasize to bone respond to 2D substrates with rigidities comparable to that of the bone microenvironment by increasing expression and production of PTHrP. The cellular response is regulated by Rho-dependent actomyosin contractility mediated by TGF-ß signaling. Inhibition of Rho-associated kinase (ROCK) using both pharmacological and genetic approaches decreased PTHrP expression. Furthermore, cells expressing a dominant negative form of the TGF-ß receptor did not respond to substrate rigidity, and inhibition of ROCK decreased PTHrP expression induced by exogenous TGF-ß. These observations suggest a role for the differential rigidity of the mineralized bone microenvironment in early stages of tumor-induced osteolysis, which is especially important in metastatic cancer since many cancers (such as those of the breast and lung) preferentially metastasize to bone

Inverse relationship of hippocampal serotonin to avoidance behavior, serotonergic activation by emotional stress differentiated by estrous cycle and surgical stress

The hippocampus is involved in learning, affect, and the neurobiology of stress. After recording individual emotional reactivity (ER) during handling for vaginal smear screening (VSS), serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), in the hypothalamus-preoptic area (HY-PA) and hippocampus were studied in two rat lines with different susceptibility to Freund's adjuvant arthritis (FAA), in relation to active avoidance behavior (AB), and under basal conditions in the FAA susceptible strain, in relation to ER, cycle stage and 20 h prior surgical stress. FAA susceptible rats compared to non-susceptible under equally low ER, showed higher AB, but lower 5-HIAA and 5-HIAA/5-HT ratio, under basal conditions, and upon termination of avoidance assay, only in hippocampus. In rats with different ER after prolonged VSS, high ER paralleled on diestrus-2 (DE-2), increased 5-HIAA and 5-HIAA/5-HT in the hippocampus and HY-PA, and adrenal weight, but decreased thymus and hippocampal weight. Under equal ER 5-HIAA and 5-HIAA/5-HT in the hippocampus and 5-HIAA/5-HT in the HY-PA were diminished on proestrus vs DE-2 but not estrus. Under equal distribution of proestrus and estrus higher ER paralleled higher hippocampal 5-HIAA. After equally high ER, combined with 20 h prior surgical stress, diminished hippocampal 5-HIAA/5-HT ratio, paralleled pronounced increase in adrenal weight compared to controls. Results suggest: negative association of hippocampal 5-HT to avoidance learning, a positive one to ER, modulated by cycle stage, and a role of differentiated 5-HT in homeostasis of HPA system. © 2002 Elsevier Science B.V. All rights reserved

The effect of sumatriptan on brain monoamines in rats

Clinical data suggests that sumatriptan is effective in the acute treatment of migraine. The vascular effects of the drug have been invoked to explain this antimigraine efficacy. However, the effect of sumatriptan on brain monoamines has not previously been investigated. In order to study these hypothetical effects, we administered the drug to 24 male rats, subcutaneously, at three doses (0.3, 0.6, and 0.9 mg/kg of body weight), and 30 minutes later, all animals were decapitated. Dopamine, serotonin, and their metabolites 3,4 dihydroxyphenylacetic acid, 5-hydroxyindoleacetic acid, and homovanillic acid concentrations were measured in the frontal cortex, hypothalamus, striatum, and hippocampus, by high performance liquid chromatography. Plasma concentrations of the drug were also determined. The control group was treated with NaCl 0.9%, given subcutaneously. Sumatriptan, at the dose of 0.3 mg/kg did not alter the brain monoamine concentrations; however, at the dose of 0.6 mg/kg, sumatriptan decreased serotonin concentration in the hypothalamus and increased the turnover of dopamine and serotonin in the hypothalamus and striatum, while at the dose of 0.9 mg/kg, it augmented only the turnover of serotonin in the hypothalamus. No dose- dependent effect of the drug was found. This subcortical antidopaminergic end antiserotoninergic effect of sumatriptan may be involved in its antimigraine action

Monoaminergic dysregulation on diestrus-2 and estrus through high emotional reactivity

Rats with great differences in emotional reactivity, during weighing and handling for vaginal smear screening were examined on diestrus-2 (DE-2), proestrus (PE), and estrus (E). Rats with high emotional reactivity (HR), interpreted as trait anxiety, had different serotonergic and dopaminergic profile in hypothalamus-preoptic area (HY-PA) and striatum (Str) and thymus weight lower than that found in rats with low emotional reactivity (LR). In HY-PA of rats with HR when compared to rats with LR, increased 5-hydroxyindoleacetic acid (5-HIAA), 5-HIAA/serotonin (5-HT) ratio, and 3,4-dihydroxyphenylacetic acid (DOPAC) and in Str increased DOPAC and DOPAC/dopamine (DA) ratio were found only on DE-2, paralleled by increased adrenal weight and decreased thymus weight. In Str, a significant effect of HR on 5-HIAA was found only on E, in parallel with increased 5-HT and decreased DOPAC and DOPAC/DA ratio when compared to rats with LR. The results suggest that activation of 5-HT and DA in HY-PA and DA in Str through HR is apparent only on DE-2 while, conversely, on E suppression of striatal DA it is apparent with 5-HT dysregulation. These findings might have some relevance to the predisposition of women with trait anxiety to premenstrual syndrome

Relationship between the thymus and neurochemical changes in the hypothalamus-preoptic area and prefrontal cortex in female rats with delayed puberty

In female rats, aged 55-58 days with delayed puberty due to deficient growth and environmental stress, 5-hydroxyindoleacetic acid levels and serotonin turnover rate in the hypothalamus-preoptic area as well as body weight, body weight gain and relative weight of ovaries, uterus, adrenals and preputial glands were lower while serotonin and 5-hydroxyindoleacetic acid levels in the prefrontal cortex were higher when compared to normal rats with the latest onset of puberty aged 42-52 days. In rats with delayed puberty, multiple regression analysis revealed a significant negative dependence on dopamine turnover in the hypothalamus-preoptic area for body weight gain and, of all organs, for the relative weight of the thymus. A similar negative significant dependence on serotonin turnover rate in the prefrontal cortex was also found for the relative weight of thymus and spleen. The same analysis in the opposite direction revealed a significant negative dependence of 3,4-dihydroxyphenylacetic acid levels and dopamine turnover rate in the hypothalamus-preoptic area as well as serotonin turnover rate in the prefrontal cortex only on thymus weight. After separation of delayed pubertal rats into two groups, based on absolute ovarian weight, the rats in the low ovarian weight range and no signs of puberty exhibited: lower body weight gain, lower body weight, and lower relative weight only of thymus, ovaries and preputial glands in parallel with an increased dopamine turnover rate in the hypothalamus-preoptic area and serotonin turnover rate in the prefrontal cortex compared to the delayed pubertal rats in the high oval-lan weight range and early signs of puberty. The results suggest that in rats with delayed puberty: (1) serotonergic activation in the hypothalamus-preoptic area is lower compared to normal puberty rats; (2) dopaminergic activation in the hypothalamus-preoptic area negatively affects body weight gain, thymus weight and initiation of puberty and (3) thymus weight is negatively implicated in dopaminergic activation in the hypothalamus-preoptic area and serotonergic activation in the prefrontal cortex and positively related to ovarian weight and early signs of puberty, (C) 1997 ISDN. Published by Elsevier Science Ltd

The neurochemical effects on striatal dopamine turnover rate of N-stearyl dopamine, after acute administration in rats

1. Considerable efforrts have been made in order to develop autoreceptor selective agonists for the treatment of schizophrenia and hyperkinetic disorders. 2. Recent behavioural studies showed that the newly synthesized dopamine lipoamide, N-stearyl dopamine induced a strong hypomotility (-80%) in rats and mice. It is worth noting that this behavioural response was partially antagonized by dopaminergic antagonists, such as haloperidol and sulpiride, administered at doses that block DA autoreceptors. 3. In the present study the authors investigated the neurochemical changes induced by S-DA, in the striatum of the rat brain, in order to estimate a possible correlation between the above mentioned behavioural response and DA metabolism. 4. S-DA (10 or 100mg/kg, i.p.) induced a significant decrease in DA turnover rate while it did not affect 5-HT metabolism in the striatum. 5. Considering that S-DA induces a strong hypomotility, which can be partially antagonized by haloperidol or sulpiride administered at low doses, while also decreases the striatal DA turnover rate, it could be suggested that together these findings indicate that this DA lipoamide may be display the characteristics of an antipsychotic agent, acting on the "DA selective" autoreceptors