Comptes rendus des seances de la Societe de biologie et de ses filiales最新文献

The purpose of this study was to observe the recovery of maximal strength immediately after a maximal eccentric strength training set. The trained female subjects (n = 8) performed 10 bouts of 10 maximal eccentric contractions of the quadriceps muscle. Each bout was separated by a 2 minutes rest period. Integrated electromyogram (iEMG) of the vastus medialis and the rectus femoris, and torque were measured before, just after, 24 and 48 hours after training session, at different knee angular velocity (-60, 0, 60, 120, and 240 degrees.s-1). Possible structural damage of the muscular cell were searched from the urinary concentration of some protein catabolism metabolites before (basal rate), 24 and 48 hours after the exercise. Maximal torque significantly fell for any angular velocity immediately after the training session: 13.6% at -60 degrees.s-1, 16.9% at 60 degrees.s-1, 7.5% at 120 degrees.s-1, 12.8% at 240 degrees.s-1 and 8.6% at 0 degree.s-1. This event was accompanied by an increase of the iEMG at the training angular speed, and by an increase of the metabolites concentration in a half part of the subjects. Strength developed during eccentric contraction showed the earliest recovery. And it even significantly overshot its initial level by 14.9% at 48 hours. A significant increase of the iEMG assessed at the eccentric velocity was then observed. In the same time, 3 of the 6 subjects showed an increase of their urinary concentration of the chosen metabolites in comparison with their initial values. This result may closely be connected with the supercompensation phenomenon, which first appears in the training mode. This phenomenon could partly be explained by the associated increase of the iEMG.

Compared to others species Homo sapiens is physically underprivileged as much by his relative weakness than by his lack of natural defense. Only his mental abilities allowed him to cope with the various dangers which threaten him and to rule over the biosphere that he managed to modified for his own benefit. The neolithic revolution which saw the generalization of agriculture and the breeding of animals offered a considerable quantities of resources which lead to a strong demographic growth. All this produced a successions of discoveries which improved his quality of life. Today after an era of quantitative growth the production of the agroalimentary sector enter a qualitative period in which the aim is note only to increase the production of the traditional resources but, by the alteration of the genetic heritage, to improve their properties.

Having reported that HIV-1-infected T cell lines are rescued as CD4- from cytolysis by human complement factor B, we now show the presence of an in vivo counterpart of such CD4- T cells by demonstrating the circulating CD3+ CD4- CD8- CD29+ cells in the blood of seropositive subjects (n = 91, classified by the immunologic scale scores 0, 1, 2 and 3). The cell population was found to be significantly increased in the early phase of infection in score 0: 195/mm3 (p < 0.005) and in score 1:376/mm3 (p = 0.001). With the infection progressing to score 2, the cells decreased to 220/mm3 (p < 0.001) and finally to the same range: 101/mm3, as that of uninfected subjects. Further elucidation of the mechanism of the appearance and disappearance of that population in vivo could help to elucidate protective immunologic processes.

We have investigated the induction of epidermal growth factor (EGF) in the urogenital sinus of fetal mice when the sinuses were cultured with testosterone. Immunofluorescence study revealed that almost no EGF is detectable in the pre-incubated sinuses, whereas EGF is induced in the sinus mesenchyme as early as 2 hours after the testosterone treatment. The results support the hypothesis that paracrine-like factors secreted from the sinus mesenchyme activated by androgens may be EGF or EGF-like growth factors that stimulate the sinus epithelium to induce prostatic buds.

For a long time, extracellular proteinases were thought to be expressed by the cancerous cells and only able to cleave extracellular matrix components, in order to promote tumor cell invasion. Recent works have now demonstrated that these proteinases are currently synthesized by stromal fibroblastic cells and that some of them may exhibit additive function(s). These findings lead to a new therapeutical concept leading to target the activity of stromal proteinases, and most notably of the matrix metalloproteinases.

To maintain their body integrity when aggressed, living organisms use a series of genetic and metabolic events constituting the stress response. Experiments carried out on man and superior vertebrates have shown that the stress response can be considered as a general adaptative syndrome. It constitutes one of the key elements of the defense system and can schematically be decomposed as an immediate response related to the release of preformed or formed de novo cytotoxic cell mediators and a delayed response with genomic interactions and induced protein synthesis. In invertebrates, experiments were essentially aimed at study of cytotoxic secreted agents during immediate response. However, the presence of cytokine like agents, NO-synthases and heat shock proteins were also found in molluscs, insects, annelids and echinoderrns. In marine bivalvia, informations on stress response are scarce and ftagmentary and, to the best of our knowledge, no coherent synthesis was carried out. The aim of the present work is to collect up to date results in this field and to carry out a comparative analysis of defense mechanisms known in vertebrates.

Glucocorticoids are physiological molecules that are also extensively used in clinics as anti-inflammatory, immunosuppressive or anti-tumoral agents. Glucocorticoids can induce apoptosis on normal lymphoid cells and play a key role in the physiology of thymic selection. In clinics these molecules are also used for their potencies in inducing apoptosis of malignant lymphoid cells. Glucocorticoids are mediating their effects after binding to an intracellular receptor belonging to the steroid receptor superfamily: the glucocorticoid receptor (GR). Once activated, the GR, can mediate his effects through direct binding on the DNA or via protein/protein interactions with transcription factors. Depending on the type of lymphocytes, the mechanism of apoptosis induced by glucocorticoids fall roughly in two categories: induction of "death genes" by the activated GR (I kappa B, c-jun) or repression of survival factors (AP-1, c-Myc). In the case of thymic selection the mechanism is more subtle depending on the mutual repression of Nur77 and GR.

Apoptosis is a genetically programmed cell death that is required for morphogenesis during embryogenic development and for tissue homeostasis in adult organisms. In most cases, apoptosis involves cytochrome c release from mitochondria. In the cytosol, cytochrome c combines with APAF-1 in the presence of ATP to activate caspase-9 that, in turn, activates effectors caspases such as caspase-3. Bcl-2 and related proteins control cytochrome c release from the mitochondria whereas IAP (for Inhibitor of APoptosis) molecules modulate the activity of caspases. Plasma membrane receptors such as Fas (CD95, APO-1), characterized by a so-called "death domain" in their cytoplasmic domain, can activate the caspase cascade through adaptator molecules such as FADD (Fas-Associated protein with a Death Domain). Dysregulation of the apoptotic machinery plays a role in the pathogenesis of various diseases and molecules involved in cell death pathways are potential therapeutic targets in immunologic, neurologic, cancer, infectious and inflammatory diseases.

Peptidic toxins extracted from spider, marine snails or snakes venoms, have considerably helped the pharmacological characterization of calcium channels. They have successfully been used for calcium channels mapping. However, the actual situation remains unclear. Genetic investigations demonstrated the existence of a great number of types or sub-types of calcium channels. In recent year a large number of toxins have been purified. Many of these toxins have specific actions on calcium channels and have been used as powerful tools in pharmacological approaches of calcium channels. However the pharmacology of the calcium channels remains very limited, many of them are waiting for the discovery of pharmacological tools allowing their molecular approach in order to determinate their biological implications. In this paper we describe the different families of calcium channels and toxins that interact with these channels. We also recapitulate the "non defined" calcium channels i.e. calcium channel which does not correspond to a N, L, P/Q, R or T type channel and for which no effector are available. We report the discovery and characterization of mapacalcine, a toxin extracted for a marine sponge, as an example of an approach of an undefined calcium channels first characterized by electrophysiological techniques and for which a specific toxin has been purified allowing its pharmacological approach. We also state the possible role of calcium channel toxins in the domain of therapeutic applications.