The acute inhibition of rapid eye movement sleep by citalopram may impair spatial learning and passive avoidance in mice.

Rapid eye movement (REM) sleep is known to be essential for memory. Hence, REM sleep deprivation impairs memory processes. The frequently prescribed selective serotonin reuptake inhibitors (SSRIs) are known to cause REM sleep deprivation and to impair cognitive performance in humans and rodents. We suggested that impaired memory processes by citalopram in C57/BL6 mice could be explained by the acute inhibition of REM sleep. We hypothesized that those acute citalopram 5 and 10 mg/kg injections induced REM sleep deprivation, altered cognitive performance in passive avoidance, impaired spatial memory compared to controls. Three experiments have been realized: (1) mice received successively physiological saline, injection of citalopram 5 and 10 mg/kg and were recorded by polysomnographic recording after each injection. (2) Cognitive performance was evaluated in the passive avoidance with two groups of mice. One group received citalopram before training and one, after training. (3) Spatial learning was evaluated with another group of animals in the Y-maze test. At 5 and 10 mg/kg, citalopram delayed REM sleep onset and decreased REM sleep amounts (vs. controls). The same doses were administrated in the passive avoidance test and have significantly shortened latency to enter the dark compartment. In the Y-maze, citalopram-treated mice showed a decreased percentage of time spent in the novel arm in contrast to the two other arms compared with controls. We showed that citalopram impaired cognitive performance in behavioral tasks. Those impairments could be linked to REM sleep deprivation induced by citalopram although causal relationship needs to be investigated in further studies.

Pro- and anti-angiogenic agents.

The vascular endothelium has been characterized in every organ system, and is described as a selective permeable barrier and as a dynamic and disseminated organ with endocrine function. These activities have been shown to result from the interactions of ligands with membrane-bound receptors as well as through specific junctional proteins and receptors that govern cell-cell interactions. The endothelial cells' movement (e.g., angiogenesis) has been hypothesized to occur following the release of stimuli that could promote the formation of new blood vessels. Angiogenesis has also been reported to be the continued expansion of the vascular tree in avascular regions, as a result of the sprouting of endothelial cells from existing vessels. Most commonly, angiogenesis has been characterized during wound healing and tumour growth. Herein we summarize and discuss the latest results from fundamental laboratory research aimed at proving a link between the proliferation of cancer and angiogenesis, as well as the new rationale around novel pro- and anti-angiogenic molecules.

Tetraiodothyroacetic acid (tetrac) and nanoparticulate tetrac arrest growth of medullary carcinoma of the thyroid.

CONTEXT: Tetraiodothyroacetic acid (tetrac) blocks angiogenic and tumor cell proliferation actions of thyroid hormone initiated at the cell surface hormone receptor on integrin alphavbeta3. Tetrac also inhibits angiogenesis initiated by vascular endothelial growth factor and basic fibroblast growth factor. OBJECTIVE: We tested antiangiogenic and antiproliferative efficacy of tetrac and tetrac nanoparticles (tetrac NP) against human medullary thyroid carcinoma (h-MTC) implants in the chick chorioallantoic membrane (CAM) and h-MTC xenografts in the nude mouse. DESIGN: h-MTC cells were implanted in the CAM model (n = 8 per group); effects of tetrac and tetrac NP at 1 microg/CAM were determined on tumor angiogenesis and tumor growth after 8 d. h-MTC cells were also implanted sc in nude mice (n = 6 animals per group), and actions on established tumor growth of unmodified tetrac and tetrac NP ip were determined. RESULTS: In the CAM, tetrac and tetrac NP inhibited tumor growth and tumor-associated angiogenesis. In the nude mouse xenograft model, established 450-500 mm(3) h-MTC tumors were reduced in size over 21 d by both tetrac formulations to less than the initial cell mass (100 mm(3)). Tumor tissue hemoglobin content of xenografts decreased by 66% over the course of administration of each drug. RNA microarray and quantitative real-time PCR of tumor cell mRNAs revealed that both tetrac formulations significantly induced antiangiogenic thrombospondin 1 and apoptosis activator gene expression. CONCLUSIONS: Acting via a cell surface receptor, tetrac and tetrac NP inhibit growth of h-MTC cells and associated angiogenesis in CAM and mouse xenograft models.

RPGR is mutated in patients with a complex X linked phenotype combining primary ciliary dyskinesia and retinitis pigmentosa.

INTRODUCTION: Primary ciliary dyskinesia (PCD) is a rare disease classically transmitted as an autosomal recessive trait and characterised by recurrent airway infections due to abnormal ciliary structure and function. To date, only two autosomal genes, DNAI1 and DNAH5 encoding axonemal dynein chains, have been shown to cause PCD with defective outer dynein arms. Here, we investigated one non-consanguineous family in which a woman with retinitis pigmentosa (RP) gave birth to two boys with a complex phenotype combining PCD, discovered in early childhood and characterised by partial dynein arm defects, and RP that occurred secondarily. The family history prompted us to search for an X linked gene that could account for both conditions. RESULTS: We found perfect segregation of the disease phenotype with RP3 associated markers (Xp21.1). Analysis of the retinitis pigmentosa GTPase regulator gene (RPGR) located at this locus revealed a mutation (631_IVS6+9del) in the two boys and their mother. As shown by study of RPGR transcripts expressed in nasal epithelial cells, this intragenic deletion, which leads to activation of a cryptic donor splice site, predicts a severely truncated protein. CONCLUSION: These data provide the first clear demonstration of X linked transmission of PCD. This unusual mode of inheritance of PCD in patients with particular phenotypic features (that is, partial dynein arm defects and association with RP), which should modify the current management of families affected by PCD or RP, unveils the importance of RPGR in the proper development of both respiratory ciliary structures and connecting cilia of photoreceptors.

The human dynein intermediate chain 2 gene (DNAI2): cloning, mapping, expression pattern, and evaluation as a candidate for primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is an autosomal recessive disease characterized by chronic sinusitis and bronchiectasis, and usually associated with hypofertility. Half of the patients present a situs inversus, defining the Kartagener's syndrome. This phenotype results from axonemal abnormalities of respiratory cilia and sperm flagella, i.e., mainly an absence of dynein arms. Recently, a candidate-gene approach, based on documented abnormalities of immotile strains of Chlamydomonas reinhardtii, allowed us to identify the first gene involved in PCD. Following the same strategy, we have characterized DNAI2, a human gene related to Chlamzydomonas IC69, and evaluated its possible involvement in a PCD population characterized by an absence of outer dynein arms. DNAI2, which is composed of 14 exons located at 17q25, is highly expressed in trachea and testis. No mutation was found in the DNAI2 coding sequence of the twelve patients investigated. However, ten intragenic polymorphic sites and an EcoRI RFLP have been identified, allowing the exclusion of DNAI2 in three consanguineous families.

Loss-of-function mutations in a human gene related to Chlamydomonas reinhardtii dynein IC78 result in primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a group of heterogeneous disorders of unknown origin, usually inherited as an autosomal recessive trait. Its phenotype is characterized by axonemal abnormalities of respiratory cilia and sperm tails leading to bronchiectasis and sinusitis, which are sometimes associated with situs inversus (Kartagener syndrome) and male sterility. The main ciliary defect in PCD is an absence of dynein arms. We have isolated the first gene involved in PCD, using a candidate-gene approach developed on the basis of documented abnormalities of immotile strains of Chlamydomonas reinhardtii, which carry axonemal ultrastructural defects reminiscent of PCD. Taking advantage of the evolutionary conservation of genes encoding axonemal proteins, we have isolated a human sequence (DNAI1) related to IC78, a C. reinhardtii gene encoding a dynein intermediate chain in which mutations are associated with the absence of outer dynein arms. DNAI1 is highly expressed in trachea and testis and is composed of 20 exons located at 9p13-p21. Two loss-of-function mutations of DNAI1 have been identified in a patient with PCD characterized by immotile respiratory cilia lacking outer dynein arms. In addition, we excluded linkage between this gene and similar PCD phenotypes in five other affected families, providing a clear demonstration of locus heterogeneity. These data reveal the critical role of DNAI1 in the development of human axonemal structures and open up new means for identification of additional genes involved in related developmental defects.

Heterogeneity of the high molecular weight tau proteins in N115 neuroblastoma cells.

The sequence of a high molecular weight (HMW) tau cDNA cloned from a neuroblastoma N115 library contains, in addition to the C- and N-terminal and middle regions present in the low molecular weight mouse brain tau proteins, a 711-bp nonhomologous domain (exon 4a) and a region of 198 bp corresponding to exon 6 of the tau gene. Protein immunoblot analysis, performed with antibodies specific either for a sequence present in the N-terminal region of all the tau variants or for exon 4a revealed several bands suggesting that more than one tau form is expressed in this cell line. Northern blot experiments performed with a number of cDNA probes spanning domains common and uncommon to low molecular weight and HMW tau allowed the identification of four tau transcripts differing in the size of their coding and noncoding regions. All these transcripts contain the sequence encoded by exon 6, but two of them lack exon 4a. As shown by RNase protection assays, the N-terminal region of these transcripts is also variable and contains either exon 1, or exons 1 and 2, or exons 1-3. Yet all these HMW tau forms contain four homologous repeats in their C-terminal domain both in the differentiated and nondifferentiated cells, i.e., have adult characteristics. In conclusion, the data reported in this article demonstrate that several HMW tau variants are expressed in neuroblastoma N115 cells and that the transition between immature to mature tau forms occurring during brain development is not required for neurite outgrowth during morphological differentiation of this cell line.

[High molecular weight tau proteins and acquisition of neuronal polarity in peripheral nervous system]. / Protéines tau de haut poids moléculaire et acquisition de la polarité neuronale dans le système nerveux périphérique.

Several variants of the microtubule-associated tau proteins, are expressed during brain development and in adulthood. These entities are required to define the polarity of the neuron and the architecture of the axon but differ in sequence and in their microtubule polymerizing activity. Here, we describe a new group of high molecular weight tau proteins that contain one or two additional exons of 711 and 198 bp in their middle region and a variable N-terminal domain. These high molecular weight tau variants are preferentially expressed in the peripheral nervous system. Immunohistochemical studies showed that they are also present in the dorsal horn of the spinal cord where they are probably transported by sensory fibers arising in the periphery. However, a minor fraction of these proteins is present in the motor neurons of the ventral horn. Similar studies were performed with the neuroblastoma N115 cell line which can be differentiated in vitro and expresses only high molecular weight tau forms. In the non differentiated cells, tau antibodies label the domain of the cell body localized around the centrosome whereas, after differentiation, the cell process facing this structure is also stained. These data suggest that axonal polarity is predetermined by the localization of tau proteins in the domain of the cell body defined by the centrosome.

Thyroid hormone effects on neuronal differentiation during brain development.

Neurite outgrowth and acquisition of neuronal polarity depend on microtubule assembly and this process is impaired when hypothyroidism is established at late fetal stages in the rat. Taking in account these observations the effects of thyroid hormone deficiency in the developing cerebellum were studied with probes for different tubulin isoforms and for two microtubule-associated proteins, tau and MAP2, which are specific for the axons and the dendrites, respectively. The results showed that thyroid hormone deficiency: 1) desynchronizes the spatio-temporal program of axonal and dendritic differentiation in the cerebellum. 2) Modifies the developmental pattern of expression of various tubulin isoforms. 3) Delays replacement of the immature tau variants by the mature forms. The adult variants of tau proteins specify adult and stable axons whereas the juvenile forms are expressed when axons are growing actively. According to these criteria the hypothyroid brain remains immature at stages when proper connectivity is normally established. Thyroid hormone appears therefore as an epigenic signal that synchronizes axonal and dendritic outgrowth, two major parameters of the construction of the neuronal network.

Regulation by thyroid hormone of microtubule assembly and neuronal differentiation.

In this review we examine successively: 1) the major effects of thyroid hormone deficiency seen during brain development with special emphasis on the changes in neuronal morphology and migration occurring postnatally in the cerebellum. 2) The effects of this hormone on microtubule assembly during neurite outgrowth and acquisition of neuronal polarity. 3) The changes in expression of the different tubulin isoforms occurring during development in the normal and hypothyroid rat brain. 4) The regulation by thyroid hormone of the transition occurring during development between the juvenile and adult microtubule-associated protein Tau.

Splicing of juvenile and adult tau mRNA variants is regulated by thyroid hormone.

The effect of thyroid hormone on the expression of tau transcripts was studied during postnatal brain development. The level of tau mRNA was only slightly changed postnatally in the cerebral hemispheres of hypothyroid rats, whereas the level of tau mRNA in the cerebellum was maintained at a higher level than in the euthyroid controls. As shown by in situ hybridization studies, such an alteration in tau mRNA expression can be ascribed to an effect of thyroid hormone on the rate of migration of the granule cells in the cerebellum; that tau mRNAs remain high in the cerebellum as long as the granule cells are migrating correlates with the observation that hypothyroidism slows the rate of migration of granule cells. RNase protection assays also showed that thyroid hormone deficiency delays the transition between the immature and mature tau transcripts in both brain regions. Thus, one of the effects of thyroid hormone is to regulate the splicing mechanism that allows replacement of the juvenile tau variants by the adult entities during neuronal differentiation.

Glutamine synthetase: a marker of an astroglial subpopulation in primary cultures of defined brain areas.

Primary cultures from various areas of newborn mouse brain were developed and characterized. Enriched astroglial cultures of the cerebral hemispheres, cerebellum, medulla oblongata and olfactory bulbs contained about 80-90% glial fibrillary acidic protein (GFA) immunolabelled cells. These cultures were composed of a majority of flat, 'protoplasmic-like' cells. The aim of this culture model was used: (1) to study glutamine synthetase (GS) activity during in vitro astroglial development; (2) to consider the hydrocortisone effect on GS activity during both growth and maturation periods, and (3) to determine the development of GS immunoreactivity in the cells and eventual GFA and GS expression in these cells. We observed that GS increased during brain maturation in vivo and in vitro, and that addition of hydrocortisone (1 microM, 48 h) to the culture medium induced varying GS activity depending on the developmental stage and the area. In the four areas studied, the number and intensity of GS-immunolabelled cells reached an optimum between 18 and 30 days in vitro. Only about 50-70% of the cell population was GS positive. Double-labelling experiments showed that three groups of cells coexist whatever the considered area. Two expressed both GFA and GS proteins, the last marker at either a low or a high level, and the third was devoid of GS immunoreactivity. Regional differences in GS-specific activity, GS inducibility and GS immunoreactivity exist in the astroglial population, but the factors responsible for these variations are not yet known.

Protein synthesis in astrocytes: 'spontaneous' and cyclic AMP-induced differentiation.

Primary cultures of mouse astrocytes have been used to study astroglial protein synthesis during 'in vitro' differentiation. Spontaneous age-related differentiation was compared to the effect of DBcAMP or forskolin, a drug which directly stimulates the adenylate cyclase and induces 'morphological differentiation' in these cells. Cell differentiation was followed in parallel by phase contrast microscopy and immunofluorescence techniques. Two antisera, one raised against GFA, the other against microtubule-associated protein 2 (MAP2) were used. Anti-GFA serum labelled the cells as early as 7 days in vitro. Anti-MAP2 serum revealed a dense fibrous network at later stages of the culture, whereas the dividing astroblasts appeared poorly stained by this antibody. Both phase contrast microscopy and immunofluorescence techniques suggested that most of the cells spontaneously differentiate after 3 weeks of culture even in the absence of DBcAMP or forskolin. Forskolin, while accelerating differentiation after 7 days of culture, produced smaller cells than DBcAMP and had biphasic effects on cell morphology. Mono- and two-dimensional gel electrophoresis of the 35S-methionine labelled cells also showed that the major changes in protein synthetic activity occur spontaneously during the time course of the culture. Whatever the stage of the culture, DBcAMP or forskolin induced changes in the synthesis of only a few proteins. However, depending on the culture stage the proteins, which were positively or negatively controlled by these drugs, were not the same.

Microtubule-associated proteins and in vitro astrocyte differentiation.

Primary cultures of mouse brain astrocytes have been used to identify the microtubule-associated proteins (MAPs) present in this cell type at different stages of in vitro differentiation. The MAPs of the astrocyte have been identified by polyacrylamide gel electrophoresis and immunological detection. Two antisera were raised against two brain MAPs, tau and MAP-2. These antisera were also used to label the microtubular network in the intact astrocytes at different stages of the culture. The mature astrocyte contains a variety of MAP-like proteins. Anti-MAP-2 serum detected several proteins of high molecular weight (380,000, 260,000, 205,000 and 165,000 mol wt) and one microheterogeneous peak of 83,000 mol wt. Anti-tau also detected high molecular weight components (380,000 to approximately 200,000 mol wt) but not the 165,000-mol-wt peak; in addition two microheterogeneous peaks of 83,000 and 62,000 mol wt were detected by the anti-tau serum. The 62,000-mol-wt peak was therefore detected only by the anti-tau serum whereas the 83,000-mol-wt component cross-reacted with both antisera. At early stages of the culture the immature cell contained about two times less immunoreactive material than at mature stages. Qualitative changes of the high molecular weight components were also observed. In the intact cell both antisera revealed a dense fibrous network. At early stages of the culture the astroblasts were stained by the antisera but the reaction was very diffuse in the cytoplasm; few fibrous cells were intensively stained. Morphological differentiation, which began after serum deprivation and which was accelerated by forskolin (a drug that induces cyclic AMP accumulation), led to high labeling of both the cell body and the cellular processes. In the presence of colchicine the staining regressed, the processes shortened, and the cell returned to a less-apparently differentiated state.

Initial rate of cholesterol esterification association with high density lipoproteins in human plasma.

The enzyme lecithin:cholesterol acyl transferase has been measured both in total plasma and in the fraction of plasma from which very low and low density lipoproteins have been removed by ultracentrifugation. The correlation between the activity of the enzyme and the free cholesterol concentration was positive in whole plasma and negative in apoB-deficient plasma. On the other hand, the positive correlation between plasma triglycerides and cholesterol esterification was not changed by the removal of apoB-containing lipoproteins. Subjects with the highest levels of high density lipoprotein cholesterol were found to have the lowest enzyme activity, but this correlation was disclosed only in apoB-deficient plasma. This inverse relationship was abolished when the enzyme activity was measured in the absence of all lipoproteins with a density less than 1.125 g/ml. Cholesterol esterification, when determined after removal of lipoproteins with a density less than 1.063 g/ml, was negatively correlated with the in vivo plasma concentration of lipoproteins in the density range 1.063-1.125 g/ml. The same results were obtained in vitro by addition of increasing amounts of this class of high density lipoproteins either in total plasma or in the ultracentrifuged fractions of plasma. This provides further evidence that the lighter density class of high density lipoproteins inhibits the enzyme reaction under physiological conditions.