Determinants of primary healthcare seeking behaviours for children during the first 18 months of life in Benin.

Background: Primary healthcare is a key element of management of childhood illness in Africa. The objectives were to identify primary care seeking determinants among infants and young children up to 18 mo in a birth cohort from Benin. Methods: From 2007 to 2009 in Benin, a birth cohort was followed until the age of 18 mo in three health centres. Multilevel Poisson regression models were fitted to identify the factors related to the monthly number of consultations. Maternal and newborn characteristics and infant general health parameters were considered. Results: A total of 566 children were followed. On average, 0.46 consultations per month per child were recorded. The number of consultations was significantly lower after the first 6 mo of life (p<0.001). A distance >1000 m was associated with fewer consultations (p=0.01). Primiparity was significantly associated with higher care seeking (relative risk 1.17 [95% CI 1.05 to 1.30], p<0.01). No child characteristics at birth were significantly associated with the number of consultations (all p>0.16). Conclusions: Development of health structures and improvement of access remain important goals for strengthening of the primary care health system. Studying factors of care seeking behaviour, like parity, can help to identify women more prone to seek care for their child during the first year of life.

[Nosocomial Burkholderia cepacia outbreak in an intensive pediatric care unit]. / Epidémie nosocomiale à Burkholderia cepacia dans une unité de réanimation infantile.

BACKGROUND: We report an outbreak of Burkholderia cepacia respiratory tract infection and colonization in an intensive pediatric care unit.P PATIENTS AND METHODS: Between February and December 1999, B. cepacia was isolated from five children hospitalized in this unit. We reviewed the charts of the patients, evaluated the antiseptics use and the disinfection practices for reusable patient care equipment. An environmental study was conducted and comparison of B. cepacia was performed with genotypic method (RAPD). RESULTS: All patients were mechanically ventilated and had received large spectrum antibiotics. The disinfection procedure for reusable equipment was not respected and some single-dose of antiseptics solutions were used for several patients. B. cepacia was not found in 34 environmental samples. The RAPD assay revealed that all five isolates had identical DNA profiles. CONCLUSION: Despite the investigation the source of the B. cepacia clone in this nosocomial outbreak remained unknown, but antiseptics use and disinfection practices were revised. No new B. cepacia infections were identified after control measures were implemented.

Regional brain cytochrome oxidase activity in beta-amyloid precursor protein transgenic mice with the Swedish mutation.

Cytochrome oxidase activity was examined in a transgenic mouse model of Alzheimer's disease with overexpression of the 751 amino acid isoform of beta-amyloid precursor protein with the Swedish mutation under control of the murine thy-1 promoter. The neuritic plaques, abundantly localized in the hippocampus and anterior neocortical areas, showed a core devoid of enzymatic activity surrounded by higher cytochrome oxidase activity at the sites of the dystrophic neurites and activated glial cells. Quantitative measures, taken only in the healthy-appearing regional areas without neuritic plaques, were higher in numerous limbic and non-limbic regions of transgenic mice in comparison with controls. Enzymatic activity was higher in the dentate gyrus and CA2-CA3 region of the hippocampus, the anterior cingulate and primary visual cortex, two olfactory structures, the ventral part of the neostriatum, the parafascicularis nucleus of the thalamus, and the subthalamic nucleus. Brainstem regions anatomically related with altered forebrain regions were more heavily labeled as well, including the substantia nigra, the periaqueductal gray, the superior colliculus, the medial raphe, the locus coeruleus and the adjacent parabrachial nucleus, as well as the pontine nuclei, red nucleus, and trigeminal motor nucleus. Functional brain organization is discussed in the context of Alzheimer's disease. Although hypometabolism is generally observed in this pathology, the increased cytochrome oxidase activity obtained in these transgenic mice can be the result of a functional compensation on the surviving neurons, or of an early mitochondrial alteration related to increased oxidative damage.

Progressive age-related impairment of cognitive behavior in APP23 transgenic mice.

Transgenic APP23 mice expressing human APP(751) with the K670N/M671L mutation, were compared at ages 3, 18 or 25 months to non-transgenic littermates in passive avoidance and in a small and large Morris maze. The task in the smaller pool habituated their flight response to the platform. Impairments in passive avoidance and small pool performance in APP23 mice were clearly age-related. In the larger Morris maze APP23 mice at all ages were impaired in latency and distance swum before finding the platform. Identical performance of 18-month APP23 and controls in a visible platform condition indicates that the Morris maze performance deficit was not due to sensory, motor or motivational alterations. At age 3 months both groups initially unexpectedly avoided the visible platform, suggesting that in young mice neophobia may contribute significantly to performance in cognitive tests. In conclusion, APP23 mice exhibit both early behavioral impairment in the large Morris maze as well as impairments in passive avoidance and small pool performance that are marked only in old age.

Spatial learning, exploration, anxiety, and motor coordination in female APP23 transgenic mice with the Swedish mutation.

Transgenic mice overexpressing the betaAPP gene with the Swedish mutation under the control of the murine thy-1 promoter show Alzheimer-like characteristics including the accumulation of Abeta protein in the cerebral cortex. Female 16-month-old APP23 transgenic mice were compared to age-matched non-transgenic mice in behavioral tests measuring spatial learning, exploration of environmental stimuli, anxiety, and motor coordination. APP23 transgenic mice had fewer fast ambulatory movements, either fast or slow stereotypy movements, and slow rears in a photocell activity chamber. The acquisition of spatial learning in the Morris water maze was impaired in APP23 transgenic mice, but not during the probe test or while swimming towards a visible platform. Neither were there intergroup differences in tests of anxiety or motor coordination. These results indicate that a learning deficit and hypoactivity, concordant with the early stages of Alzheimer's disease, characterize this mouse model with Abeta accumulation.

Impaired hypoxic tolerance and altered protein binding of NADH in presymptomatic APP23 transgenic mice.

It is being discussed whether impairment of energy metabolism is a final common pathway of neurodegeneration or initiates the neurodegenerative cascade. The goal was to investigate hypoxic tolerance and oxidative energy metabolism in 4-month-old, presymptomatic B6-Tg(ThylAPP)23Sdz (APP23) mice, a transgenic mouse model of Alzheimer's disease. Posthypoxic recovery of the population spike amplitude in hippocampal region CA1 upon stimulation of Schaffer collaterals in region CA3 (15 min hypoxia, 45 min recovery) was 43+/-46% (mean+/-S.D.) vs. 19+/-35% (P<0.05) in slices from wild-type and transgenic animals, respectively. Fluorescence lifetime sensitive spectroscopy of NADH in the CA1 pyramidal cell layer (gate set for detection of protein-bound NADH) showed a wavelength maximum at 455.3+/-1.6 nm (mean+/-S.D.) in controls and 453.5+/-2.4 nm (P<0.05) in mutants. We conclude that hypoxic tolerance is impaired in presymptomatic APP23 mice and occurs prior to extracellular deposition of amyloid plaques. Impaired energy metabolism may thus partake in initiating the neurodegenerative cascade in a transgenic model of Alzheimer's disease. The blue shift of the spectrum of NADH in mutant mice indicates an altered protein microenvironment of energy metabolism under control conditions.

Comparative analysis of amyloid-beta chemical structure and amyloid plaque morphology of transgenic mouse and Alzheimer's disease brains.

We have undertaken an integrated chemical and morphological comparison of the amyloid-beta (Abeta) molecules and the amyloid plaques present in the brains of APP23 transgenic (tg) mice and human Alzheimer's disease (AD) patients. Despite an apparent overall structural resemblance to AD pathology, our detailed chemical analyses revealed that although the amyloid plaques characteristic of AD contain cores that are highly resistant to chemical and physical disruption, the tg mice produced amyloid cores that were completely soluble in buffers containing SDS. Abeta chemical alterations account for the extreme stability of AD plaque core amyloid. The corresponding lack of post-translational modifications such as N-terminal degradation, isomerization, racemization, pyroglutamyl formation, oxidation, and covalently linked dimers in tg mouse Abeta provides an explanation for the differences in solubility between human AD and the APP23 tg mouse plaques. We hypothesize either that insufficient time is available for Abeta structural modifications or that the complex species-specific environment of the human disease is not precisely replicated in the tg mice. The appraisal of therapeutic agents or protocols in these animal models must be judged in the context of the lack of complete equivalence between the transgenic mouse plaques and the human AD lesions.

The evolution of A beta peptide burden in the APP23 transgenic mice: implications for A beta deposition in Alzheimer disease.

BACKGROUND: High levels of A beta in the cerebral cortex distinguish demented Alzheimer's disease (AD) from nondemented elderly individuals, suggesting that decreased amyloid-beta (A beta) peptide clearance from the brain is a key precipitating factor in AD. MATERIALS AND METHODS: The levels of A beta in brain and plasma as well as apolipoprotein E (ApoE) in brain were investigated by enzyme-linked immunosorbent assay (ELISA) and Western blotting at various times during the life span of the APP23 transgenic (Tg) and control mice. Histochemistry and immunocytochemistry were used to assess the morphologic characteristics of the brain parenchymal and cerebrovascular amyloid deposits and the intracellular amyloid precursor protein (APP) deposits in the APP23 Tg mice. RESULTS: No significant differences were found in the plasma levels of A beta between the APP23 Tg and control mice from 2-20 months of age. In contrast, soluble A beta levels in the brain were continually elevated, increasing 4-fold at 2 months and 33-fold in the APP23 Tg mice at 20 months of age when compared to the control mice. Soluble A beta42 was about 60% higher than A beta40. In the APP23 Tg mice, insoluble A beta40 remained at basal levels in the brain until 9 months and then rose to 680 microg/g cortex by 20 months. Insoluble A beta40 was negligible in non-Tg mice at all ages. Insoluble A beta42 in APP23 Tg mice rose to 60 microg/g cortex at 20 months, representing 24 times the control A beta42 levels. Elevated levels of ApoE in the brain were observed in the APP23 Tg mice at 2 months of age, becoming substantially higher by 20 months. ApoE colocalized with A beta in the plaques. Beta-amyloid precursor protein (betaAPP) deposits were detected within the neuronal cytoplasm from 4 months of age onward. Amyloid angiopathy in the APP23 Tg mice increased markedly with age, being by far more severe than in the Tg2576 mice. CONCLUSIONS: We suggest that the APP23 Tg mouse may develop an earlier blockage in A beta clearance than the Tg2576 mice, resulting in a more severe accumulation of A beta in the perivascular drainage pathways and in the brain. Both Tg mice reflect decreased A beta elimination and as models for the amyloid cascade they are useful to study AD pathophysiology and therapy.

Amyloid beta interacts with the amyloid precursor protein: a potential toxic mechanism in Alzheimer's disease.

Amyloid beta protein (Abeta) deposition in the brain is a hallmark of Alzheimer's disease (AD). The fibrillar form of Abeta is neurotoxic, although the mechanism of its toxicity is unknown. We showed that conversion of Abeta to the fibrillar form markedly increased binding to specific neuronal membrane proteins, including amyloid precursor protein (APP). Nanomolar concentrations of fibrillar Abeta bound cell-surface holo-APP in cortical neurons. Reduced vulnerability of cultured APP-null neurons to Abeta neurotoxicity suggested that Abeta neurotoxicity involves APP. Thus Abeta toxicity may be mediated by the interaction of fibrillar Abeta with neuronal membrane proteins, notably APP. An Abeta-APP interaction reminiscent of the pathogenic mechanism of prions may thus contribute to neuronal degeneration in AD.

Transgenic approaches to model Alzheimer's disease.

Two transgenic mouse lines were generated which express human APP751 containing familial Alzheimer's disease (AD) mutations in brain neurons. These mice develop pathological features reminiscent of AD. The degree of pathology depends on both expression levels and specific mutations. In mice with more advanced pathology (APP 23), typical plaques appear at six months which increase with age and are Congo Red positive at first detection. These congophilic plaques are accompanied by neuritic changes and dystrophic cholinergic fibers. Furthermore, inflammatory processes indicated by a massive glial reaction are apparent. Most notably, plaques are immunoreactive for hyperphosphorylated tau, reminiscent of early tau pathology. A quantitative analysis of degenerative changes by state-of-the-art unbiased stereological methods revealed a significant reduction in neuronal cell bodies of the CA1 field of the hippocampus when compared to controls. This reduction is directly related to plaque load. When subjected to analysis in the Morris water maze, 18 month old APP 23 mice show a significant increase in platform finding latency throughout the entire trial when compared to non-transgenic littermates.

Pathogenic mechanisms of Alzheimer's disease analyzed in the APP23 transgenic mouse model.

APP23 transgenic mice overexpress human APP with the Swedish double mutation. The mice start to develop amyloid plaque pathology at about six months of age, followed somewhat later by vascular amyloid deposits. Plaques are mostly of the compact type and increase exponentially during aging. Female mice show a slightly more rapid A beta plaque deposition than do male animals. Associated with the amyloid are inflammatory reactions, neuritic and synaptic degeneration as well as tau hyperphosphorylation. Older mice have a reduced cholinergic fiber length and a reduced neuron number in the hippocampal CA1 region. Crossbreeding with transgenic mice expressing human presenilin 1 carrying Alzheimer's disease-linked mutations lead to an enhancement of the pathology. The APP23 line is a suitable model to analyze the contribution of APP, A beta, and amyloid to the pathogenesis of Alzheimer's disease.

Neuronal overexpression of mutant amyloid precursor protein results in prominent deposition of cerebrovascular amyloid.

Transgenic mice that overexpress mutant human amyloid precursor protein (APP) exhibit one hallmark of Alzheimer's disease pathology, namely the extracellular deposition of amyloid plaques. Here, we describe significant deposition of amyloid beta (Abeta) in the cerebral vasculature [cerebral amyloid angiopathy (CAA)] in aging APP23 mice that had striking similarities to that observed in human aging and Alzheimer's disease. Amyloid deposition occurred preferentially in arterioles and capillaries and within individual vessels showed a wide heterogeneity (ranging from a thin ring of amyloid in the vessel wall to large plaque-like extrusions into the neuropil). CAA was associated with local neuron loss, synaptic abnormalities, microglial activation, and microhemorrhage. Although several factors may contribute to CAA in humans, the neuronal origin of transgenic APP, high levels of Abeta in cerebrospinal fluid, and regional localization of CAA in APP23 mice suggest transport and drainage pathways rather than local production or blood uptake of Abeta as a primary mechanism underlying cerebrovascular amyloid formation. APP23 mice on an App-null background developed a similar degree of both plaques and CAA, providing further evidence that a neuronal source of APP/Abeta is sufficient to induce cerebrovascular amyloid and associated neurodegeneration.

Transgenic animals in Alzheimer's disease research.

Alzheimer's disease (AD) is a neurodegenerative disorder of the brain accounting for about 50-70% of the typical late onset cases of dementia. The pathological and diagnostic hallmarks of the disease are principally the presence of extracellular deposits called neuritic amyloid plaques and the intracellular aggregation of neurofibrillary tangles. In addition selective neuronal cell loss accompanied by cerebrovascular amyloidosis is detectable. In the case of familial AD, defects in at least three different genes (APP, PS1, PS2) leading to indistinguishable pathology are now well defined. There is as yet no real treatment for AD. Therefore the availability of an easily manipulable animal model is crucial for the development of new drugs, which could slow down or, even better, stop the progression of the disease. The development and originality of such experimental models that could greatly facilitate the investigation of the aetiology and pathogenesis of AD are described and discussed in this review. They are based mainly on the attempt to reproduce the neurofibrillary tangles or the amyloid deposits and plaque formation.

Destabilization of beta-catenin by mutations in presenilin-1 potentiates neuronal apoptosis.

Mutations of the presenilin-1 gene are a major cause of familial early-onset Alzheimer's disease. Presenilin-1 can associate with members of the catenin family of signalling proteins, but the significance of this association is unknown. Here we show that presenilin-1 forms a complex with beta-catenin in vivo that increases beta-catenin stability. Pathogenic mutations in the presenilin-1 gene reduce the ability of presenilin-1 to stabilize beta-catenin, and lead to increased degradation of beta-catenin in the brains of transgenic mice. Moreover, beta-catenin levels are markedly reduced in the brains of Alzheimer's disease patients with presenilin-1 mutations. Loss of beta-catenin signalling increases neuronal vulnerability to apoptosis induced by amyloid-beta protein. Thus, mutations in presenilin-1 may increase neuronal apoptosis by altering the stability of beta-catenin, predisposing individuals to early-onset Alzheimer's disease.

Two amyloid precursor protein transgenic mouse models with Alzheimer disease-like pathology.

Mutations in the amyloid precursor protein (APP) gene cause early-onset familial Alzheimer disease (AD) by affecting the formation of the amyloid beta (A beta) peptide, the major constituent of AD plaques. We expressed human APP751 containing these mutations in the brains of transgenic mice. Two transgenic mouse lines develop pathological features reminiscent of AD. The degree of pathology depends on expression levels and specific mutations. A 2-fold overexpression of human APP with the Swedish double mutation at positions 670/671 combined with the V717I mutation causes A beta deposition in neocortex and hippocampus of 18-month-old transgenic mice. The deposits are mostly of the diffuse type; however, some congophilic plaques can be detected. In mice with 7-fold overexpression of human APP harboring the Swedish mutation alone, typical plaques appear at 6 months, which increase with age and are Congo Red-positive at first detection. These congophilic plaques are accompanied by neuritic changes and dystrophic cholinergic fibers. Furthermore, inflammatory processes indicated by a massive glial reaction are apparent. Most notably, plaques are immunoreactive for hyperphosphorylated tau, reminiscent of early tau pathology. The immunoreactivity is exclusively found in congophilic senile plaques of both lines. In the higher expressing line, elevated tau phosphorylation can be demonstrated biochemically in 6-month-old animals and increases with age. These mice resemble major features of AD pathology and suggest a central role of A beta in the pathogenesis of the disease.

Distinct processing of endogenous and overexpressed recombinant presenilin 1.

The presenilin 1 (PS1) gene has been identified by positional cloning. More than 30 mutations were detected in this gene which cosegregate with Alzheimer's disease (AD). Understanding their role in disease pathogenesis requires a characterization of the PS1 protein. We have generated a set of antibodies against the three major hydrophilic domains of the deduced amino acid sequence. Analyzing cultured cells and brain samples, we identified the endogenous PS1 polypeptide as well as amino- and carboxy-terminal fragments. These metabolites were much more abundant than the full-length molecule, indicating substantial processing. Overexpression of human PS1 markedly increased the full-length polypeptide but hardly altered the amount of the metabolites. Instead, additional proteolytic fragments appeared suggesting a different metabolism of the excess PS1, which may impede studies in transfected cells. Our results indicate a tight regulation of the endogenous PS1 metabolites. PS1 and its fragments are shown to be integral membrane proteins of the endoplasmic reticulum. The mechanisms regulating the generation of the metabolites, their potential function, and role in AD remain to be studied.

Selenocysteylation in eukaryotes necessitates the uniquely long aminoacyl acceptor stem of selenocysteine tRNA(Sec).

Selenocysteine synthesis is achieved on a specific tRNA, tRNA(Sec), which is first charged with serine to yield seryl-tRNA(Sec). Eukaryotic tRNA(Sec) exhibits an aminoacyl acceptor stem with a unique length of 9 base pairs. Within this stem, two base pairs, G5a.U67b and U6.U67, drew our attention, whose non-Watson-Crick status is maintained in the course of evolution either through U6.U67 base conservation or base covariation at G5a.U67b. Single or double point mutations were performed, which modified the identity of either or both of the base pairs. Serylation by seryl-tRNA synthetase was unaffected by substitutions at either G5a.U67b or U6.U67. Instead, and quite surprisingly, changing G5a.U67b and U6.U67 to G5a-C67b/U6.G67 or G5a-C67b/C6-G67 gave rise to a tRNA(Sec) mutant exhibiting a gain of function in serylation. This finding sheds light on the negative influence born by a few base pairs in the acceptor stem of tRNA(Sec) on its serylation abilities. The tRNA(Sec) capacities to support selenocysteylation were next examined with regard to a possible role played by the two non-Watson-Crick base pairs and the unique length of the acceptor stem. It first emerges from our study that tRNA(Sec) transcribed in vitro is able to support selenocysteylation. Second, none of the point mutations engineered at G5a.U67b and/or U6.U67 significantly modified the selenocysteylation level. In contrast, reduction of the acceptor stem length to 8 base pairs led tRNA(Sec) to lose its ability to efficiently support selenocysteylation. Thus, our study provides strong evidence that the length of the acceptor stem is of prime importance for the serine to selenocysteine conversion step.

Required optical characteristics of materials for phase-shifting masks.

The reflectivity and transmission of a multiple-layer substrate are simulated to predict the optimum choice of materials for the fabrication of phase-shifting masks for optical lithography. Two types of materials are described: a transparent shifter layer with a refractive index closely matching that of quartz, and a partially transparent layer (5-15% transmission) inducing a 180° phase shift of light compared with air. A possible refractive index n and extinction coefficient k are defined, for both layers of the partially transparent material. The fabrication tolerances are calculated in terms of refractive index, extinction coefficient, and thickness accuracy. One of the major technological challenges for both material types is to control the thickness to ±2%, which is required to satisfy the phase-shifting mask specifications for deep UV lithography (±0.5% transmission control and ±4° phase control). These criteria were calculated by the simulation of the phase and transmission errors, thereby inducing a ±10% linewidth variation of the resist patterns on the wafers.

[Effect of a sanguinarine mouthwash on children with and without upper extremity motor handicap]. / Effet d'un bain de bouche a la sanguinarine chez des enfants avic et sans handicap moteur des membres superieurs.

A survey was done at the Center of Child Readaptation at Flavigny (Meurthe-et-Moselle) to determine the effect of a mouth rinse containing 0.03% sanguinaria extract, on the plaque accumulation and gingivitis of 30 children 8 to 17 years old. 13 children had a motricity handicap of their superior members and 17 did not. All subjects rinsed their mouths twice with 15 ml of solution each time. The mouth rinses were performed in the morning and in the evening during three weeks. The children were photographed and examined using the P1I and GI indices on days 0, 7, 14, 21 and 35. No statistical significant difference was observed at any moment between children with or without handicapped upper limbs. After 3 weeks of treatment the Plaque Index had decreased 47.3% and Gingival Index 55.6%.