Comptes rendus de l'Academie des sciences. Serie III, Sciences de la vie最新文献

This historical review of the Bernard-Soulier syndrome relates: (1) the first description of the disease; (2) the main data of the research from 1948 to 1982 which led to the discovery of the molecular abnormality (lack or qualitative abnormality of the platelet glycoprotein Ib) responsible for the functional disorder (defective platelet adhesion to the vascular subendothelium) which nowadays defines the disorder.

Calpains are intracellular calcium-dependent cystein proteases active at neutral pH. There have been found in human adult myogenic cells (i.e. satellite cells) 2 forms of calpains requiring either micromolar Ca2+: mu-calpain, or millimolar Ca2+: m-calpain. Calpains could be involved in both intracellular proteolysis and cytoskeleton reorganization required for myogenic cell fusion. We showed significant differences in calpains distribution during differentiation of myogenic cells. Using mono- and polyclonal antibodies against both types of calpains, we localized mu-calpain and m-calpain in cultured human satellite cells. mu-calpain was detected in the nuclei of myoblasts and in the cytoplasm of myotubes. m-calpain was only present in the cytoplasm, and was concentrated near the nuclear envelope. Biochemical assays for calpain activities showed that the amounts of these proteinases were modulated during cell growth and differentiation. m-calpain activity was high at the proliferation phase (day 4 of culture) and reached a maximum with the beginning of fusion (day 8) and decreased slightly when the number of myotubes increased (day 12). This activity profile suggests that m-calpain could play a role in the initiation of fusion of satellite cells. The activity of mu-calpain increased regularly with cell growth, the maximum being reached when the cells differentiate, i.e. when its intracellular localization shifted from the nucleus to the cytoplasm. We conclude that the activity and the intracellular localization of the 2 forms of calpains differ with the state of differentiation of myogenic cells.

The sequencing of aromatase cDNA from rabbit granulosa cells was obtained by RACE PCR. This cDNA is 2.9 kb long. The first 119 nucleotides correspond to the first untranslated exon. Nucleotides 120 to 1,629 correspond to the coding region (1,509 nucleotides) and the rest of the sequence is non coding and contains a polyadenylation signal. Translation of the cDNA sequence indicates that the protein is composed of 503 amino acids, like in human aromatase. Its molecular weight is 57.4 kDa. The alignment between the rabbit aromatase amino acid sequence and other aromatases already described in the human, mouse, rat, cow, pig, chicken, rainbow trout and teleost fish shows that the rabbit protein exhibits the highest homology with the human one (85%).

In this study, we describe the functional alterations in the host immune system that occur following acute infection with Plasmodium yoelii. Further, we have addressed the question whether the transient condition of altered immune responsiveness can be restored by a cytokine therapy. The lymphoproliferative response towards concanavalin A (Con A) or to cross-linked anti-CD3 mAb was significantly diminished in acutely infected mice compared to immune and normal animals. This condition was associated with poor production of IL-2. In vivo treatment with recombinant IL-2 (rIL-2) resulted in marked diminution of parasitemia (from 24% +/- 6% to 8% +/- 3%) in mice during the acute phase of infection. Despite this diminution in parasitemia, 70% of the IL-2 treated mice died by day 17 post infection. In vivo treatment with rIL-2 led to a partial but significant restoration in lymphoproliferative response to TCR-mediated (cross-linked anti-CD3 mAb) or to Con A-induced stimulation in acutely infected mice. The transcripts for IL-4, IL-5, GM-CSF, and TNF-alpha were expressed in the splenocytes from acutely infected mice not treated with rIL-2. mRNAs for IL-2, IFN-gamma, IL-6, IL-10 which were not detected in acutely infected mice could be reversed by administration of rIL-2 in vivo. We suggest that some of the hyporesponsive T-cells in the acute phase of infection have the potential to be reversed, and this reversal is manifested also at the level of cytokine gene expression.

The role of GP Ib-IX complexes in platelet adhesion was discovered from studies on patients with the Bernard-Soulier Syndrome (BSS). In this inherited disorder, the bulk of the platelets are round and giant. Furthermore, the platelet count is decreased, often severely so. The relationship between these abnormalities and the deficiency of GP Ib-IX is not well understood. In normal discoid platelets, the bulk of GP Ib-IX is found on the plasma membrane. After platelet activation by thrombin, this distribution changes and the majority of GP Ib-IX complexes are located within the surface-connected canalicular system (SCCS). The platelets now possess pseudopods and are spheroid. Cytoskeletal modifications accompany these changes. We now report that platelets of a BSS variant with a qualitative defect of GP Ib show no translocation of GP Ib in response to thrombin, suggesting that the linkage with the cytoskeleton is impaired. Morphological studies of megakaryocytes (MK) from BSS patients show an altered maturation and an abnormal development of the membrane systems, implying a role for GP Ib-IX in megakaryocytopoiesis. In a case of Epstein syndrome, where giant platelets and thrombocytopenia are associated with deafness and renal dysfunction, platelets possess the bulk of GP Ib-IX inside the SCCS but without signs of platelet activation as assessed by P-selectin expression. This patient also shows an impaired megakaryocytopoiesis and an irregular development of the demarcation membranes within the MK. As collagen IV mutations are a feature of the related Alport syndrome, we hypothesize that defects in the link between extracellular matrix proteins, membrane receptors and the cytoskeleton could be a common cause of giant platelet syndromes.

This paper reports the occurrence of a spongiform encephalopathy (SE) in young adult monkeys housed in a zoological park. Three rhesus monkeys (Macaca mulatta) acquired from the same zoo and maintained on feed containing animal protein, developed a progressive neurological disorder with behavioural abnormalities and physical deterioration and died at the age of 10-year-old. Neuropathological examination of one of these animals revealed a spongiform encephalopathy similar to that observed in monkeys following experimental transmission of Creutzfeldt-Jakob disease (CJD). In particular, several brain regions exhibited vacuolation of nerve cell bodies and processes accompanied by astrogliosis. Immunohistochemical analysis showed prion protein (PrP) immunoreactivity at the periphery of vacuolated neurons. The spontaneous occurrence of a SE in these young monkeys might be related to consumption of protein of animal origin.

Specific interactions between the cell surface CD4 receptor and the HIV-1 envelope glycoprotein gp120 are responsible for the entry of HIV into host cells. Following infection, a down-modulation of CD4 at the cell surface is commonly observed. This may render cells resistant to subsequent infection by HIV as well as other viruses that also use CD4 as a portal of entry. This phenomenon is termed retroviral interference. CD4 down-modulation is complex and involves at least 3 viral gene products which include the envelope precursor gp160 and 2 auxilliary proteins Nef and Vpu. CD4 down-modulation has been observed in each of primary CD4+ T-lymphocytes and monocyte-derived macrophages, as well as both T and monocytic cell lines. CD4 down-regulation may occur at different levels. Specific binding of soluble gp120 may lead to internalization of CD4. The HIV-1 nef gene product which is expressed prior to HIV-1 structural proteins also causes the internalization of CD4 followed by its lysosomal degradation. During the late phase of viral gene expression i.e. viral structural protein synthesis, CD4-gp160 complexes forming in the ER represent another important factor leading to CD4 down-modulation. Finally, CD4 which is retained by gp160 in the ER, is specifically degraded in the presence of Vpu. Thus, it appears that CD4 down-regulation is of central importance to the life cycle of HIV-1.

Regulation of proliferation and migration are well known roles of fibroblast growth factor 2 (FGF-2) for arterial smooth muscle cells (SMC). We show here, by sense cDNA transfection that endogenous FGF-2 expression controls alpha-actin level in SMC clones. All the high alpha-actin expressing clones were FGF-2 transfected. Control clones carrying a deleted vector showed a weak expression and an altered actin polymerisation compared to the parental cultures. Among FGF-2 transfected clones, alpha-actin expression was heterogenous with diversely high levels. These observations were obtained using normal rat SMC or SMC from a transformed cell line. They indicate a role for endogenous FGF-2 in arterial SMC differentiation. Our results suggest that FGF-2 might act either by permissing clonal growth of already differentiated cells or by regulating expression or stability of alpha-actin. They open new perspective for gene therapy of the arterial wall.

Photoreceptor disc shedding and their phagocytosis by the retinal pigment epithelium undergo a daily rhythm entrained by an intrinsic oscillator involving melatonin and dopamine in non-mammals. Such a mechanism is not demonstrated in mammals, but the rhythm of photoreceptor renewal can be modulated by exogenous melatonin and dopamine. The present experiments were designed to show whether a direct action of DA occurs on pigment epithelial cells, and to identify the receptor mediating this action. Primary cultures of bovine retinal pigment epithelium were incubated with bovine rod outer segments in the presence of dopamine, D1 and D2 agonists, D1 antagonist and forskolin. Dopamine, D1 agonist and forskolin decreased phagocytosis, while D2 agonist was inactive. Thus dopamine slows pigment epithelium phagocytosis in vitro through a D1 receptor. Increased phagocytosis following blockade of the receptor by an antagonist suggests a more complex modulation of phagocytosis by dopamine.

A biometric study of the somatic characteristics weight and stature carried out in 1994 on 5,751 newborn children of both sexes showed the existence of an index of corpulence of the P/T2.75 type which presents the particularity of being correlated to weight and without any link with stature, unlike Quetelet's index (P/T2) and P/T3 Roehrer's index. At fixed stature, the coefficients of the average weight variation are lower than in adults. Moreover, there is no significant difference between the average weight in boys and in girls, their fluctuations being comparable. The expression P/T2.75 allows us to compare the corpulence of newborns of both sexes having distinct weight and stature.