Dynamics of PfEMP1 Antibody Profile From Birth to 12 Months of Age in Beninese Infants.

BACKGROUND: Plasmodium falciparum-infected erythrocytes bind to specific endothelial cell receptors via members of the PfEMP1 family exported onto the erythrocyte surface. These interactions are mediated by different types of cysteine-rich interdomain region (CIDR) domains found in the N-terminal region of all PfEMP1. CIDRα1 domains bind endothelial protein C receptor (EPCR), CIDRα2-6 domains bind CD36, whereas the receptor specificity of CIDRß/γ/δ domains is unknown. METHODS: In this study, we investigated the level of immunoglobulin (Ig)G targeting the different types of PfEMP1 CIDR during the first year of life. We used plasma collected longitudinally from children of pregnant women who had been followed closely through pregnancy. RESULTS: Antibodies to CIDRα1 domains were more frequent in cord blood compared with antibodies to CIDRα2-6 domains. Higher IgG levels to EPCR-binding CIDRα1 variants positively correlated with the timing of first infections. Antibodies to all PfEMP1 types declined at similar rates to the point of disappearance over the first 6 months of life. At 12 months, children had acquired antibody to all types of CIDR domains, mostly in children with documented P falciparum infections. CONCLUSIONS: These observations agree with the notion that the timing and phenotype of first P falciparum infections in life are influenced by the immune status of the mother.

Changes in hip flexor passive compliance do not account for improvement in vertical jump performance after hip flexor static stretching.

To date, there is limited research investigating stretching of antagonist muscles and its effects on agonist muscle function. The purpose of this research was to investigate the effects of pre-static stretching (pre-SS) of the hip flexor musculature on passive hip extension range of motion (ROM) and vertical jump height. Fifteen subjects reported to the laboratory on 4 separate days (D1, D2, D3, and D4). D1 was for familiarization, while on D2 to D4, subjects randomly completed 1 of 3 intervention conditions; no stretch (CON), hip flexor stretch (HFS), or hip extensor stretch (HES). Subject's pre- and post-intervention hip extension ROM were measured before performing 3 sets of pre- and post-maximal counter-movement vertical jumps. Vertical jump height was normalized to baseline for data analysis. A repeated-measures ANOVA with post hoc paired sample t-tests revealed a significant increase in vertical jump height in the HFS condition (1.74% ± 0.73; p ≤ 0.05) when compared with CON (-1.34% ± 0.96) or HES (-1.74% ± 0.65) conditions. There was also a significant increase in hip extension ROM after the HFS stretching protocol (6.5 ± 2.75%; p ≤ 0.05) when compared with the CON protocol (-1.73 ± 3.26); however, no significant difference when compared with the HES protocol (1.84 ± 2.79). A correlation analysis showed that the relative hip laxity of each subject had no effect on response to either condition nor did the magnitude of hip ROM change predict improvement in vertical jump. These results suggest that performing SS of the hip flexors may enhance vertical jump performance independent of changes in passive compliance of the hip flexor muscular tendon unit.

[Multiple imputation of missing at random data: General points and presentation of a Monte-Carlo method]. / L'imputation multiple des données manquantes aléatoirement : concepts généraux et présentation d'une méthode Monte-Carlo.

BACKGROUND: Statistical analysis of a data set with missing data is a frequent problem to deal with in epidemiology. Methods are available to manage incomplete observations, avoiding biased estimates and improving their precision, compared to more traditional methods, such as the analysis of the sub-sample of complete observations. METHODS: One of these approaches is multiple imputation, which consists in imputing successively several values for each missing data item. Several completed data sets having the same distribution characteristics as the observed data (variability and correlations) are thus generated. Standard analyses are done separately on each completed dataset then combined to obtain a global result. In this paper, we discuss the various assumptions made on the origin of missing data (at random or not), and we present in a pragmatic way the process of multiple imputation. A recent method, Multiple Imputation by Chained Equations (MICE), based on a Monte-Carlo Markov Chain algorithm under missing at random data (MAR) hypothesis, is described. An illustrative example of the MICE method is detailed for the analysis of the relation between a dichotomous variable and two covariates presenting MAR data with no particular structure, through multivariate logistic regression. RESULTS: Compared with the original dataset without missing data, the results show a substantial improvement of the regression coefficient estimates with the MICE method, relatively to those obtained on the dataset with complete observations. CONCLUSION: This method does not require any direct assumption on joint distribution of the variables and it is presently implemented in standard statistical software (Splus, Stata). It can be used for multiple imputation of missing data of several variables with no particular structure.

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.

The subfornical organ: a central target for circulating feeding signals.

The mechanisms through which circulating ghrelin relays hunger signals to the CNS are not yet fully understood. In this study, we have examined the potential role of the subfornical organ (SFO), a circumventricular structure that lacks the normal blood-brain barrier, as a CNS site in which ghrelin acts to influence the hypothalamic centers controlling food intake. We report that ghrelin increased intracellular calcium concentrations in 28% (12 of 43) of dissociated SFO neurons and that the SFO expresses mRNA for the growth hormone secretagogue receptor. Whole-cell patch recordings from SFO neurons demonstrated that in 29% (9 of 31) of neurons tested ghrelin induced a mean depolarization of 7.4 +/- 0.69 mV, accompanied by an increase in action potential frequency. Voltage-clamp recordings revealed that ghrelin activates a putative nonselective cationic conductance. Previous reports that the satiety signal amylin exerts similar excitatory effects on SFO neurons led us to examine whether these two peptides influence different subpopulations of SFO neurons. Concentration-dependent depolarizing effects of amylin were observed in 59% (28 of 47) of SFO neurons (mean depolarization, 8.32 +/- 0.60 mV). In contrast to ghrelin, voltage-clamp recordings suggest that amylin influences a voltage-dependent current activated at depolarized potentials. We tested single SFO neurons with both peptides and identified cells responsive only to ghrelin (n = 9) and only to amylin (n = 7) but no cells that responded to both peptides. These data support a role for the SFO as a center at which ghrelin and amylin may influence separate subpopulations of neurons to influence the hypothalamic regulation of feeding.

Functional consequences of heterogeneous gap junction channel formation and its influence in health and disease.

The capacity of multiple connexins to hetero-oligomerize into functional heterogeneous gap junction channels has been demonstrated in vivo, in vitro, and in nonmammalian expression systems. These heterogeneous channels display gating activity, channel conductances, selectivity and regulatory behaviors that are sometimes not predicted by the behaviors of the corresponding homogeneous channels. Such observations suggest that heteromerization of gap junction proteins offers an efficient cellular strategy for finely regulating cell-to-cell communication. The available evidence strongly indicates that heterogeneous gap junction assembly is important to normal growth and differentiation, and may influence the appearance of several disease states. Definitive evidence that heterogeneous gap junction channels differentially regulate electrical conduction in excitable cells is absent. This review examines the prevalence, regulation, and implications of gap junction channel hetero-oligomerization.

Prokineticin 2 modulates the excitability of subfornical organ neurons.

The recent discovery of prokineticin 2 (PK2) expression in the suprachiasmatic nucleus and its receptors in critical autonomic control centers of the brain, including the subfornical organ (SFO), suggests the intriguing possibility that PK2 regulates the excitability of SFO neurons and thus influences autonomic function. Using current-clamp techniques to record from dissociated SFO neurons, we examined the effects of PK2 on the excitability of these cells. PK2 (20 nm) induced depolarizations in 40% of SFO neurons (n = 45; mean, 7.5 +/- 1.7 mV), an effect that was reversible, PK2-specific, and concentration dependent. The depolarization was accompanied by an increase in action potential frequency from 0.4 +/- 0.1 to 1.4 +/- 0.5 Hz in responding cells (n = 10). This excitatory effect appears to be, in part, attributable to a PK2-induced decrease in the delayed rectifier potassium current (I(K)). In 10 SFO neurons recorded using perforated patch voltage-clamp techniques, six demonstrated a reversible decrease in I(K) (mean decrease, 26.7 +/- 6.4%) in response to 20 nm PK2, whereas artificial CSF alone was without an effect on these currents. These data are the first to show excitatory effects of PK2 on neurons and, in addition, demonstrate that this peptide modulates voltage-activated K(+) channels. The activation of SFO neurons by PK2 illustrates a mechanism through which this peptide may exert circadian control of autonomic functions.

Reliability of goniometric and trigonometric techniques for measuring hip-extension range of motion using the modified Thomas test.

CONTEXT: Goniometric assessment of hip-extension range of motion is a standard practice in clinical rehabilitation settings. A weakness of goniometric measures is that small errors in landmarking may result in substantial measurement error. A less commonly used protocol for measuring hip range of motion involves applying trigonometric principles to the length and vertical displacement of the upper part of the lower extremity to determine hip angle; however, the reliability of this measure has never been assessed using the modified Thomas test. OBJECTIVE: To compare the intrarater and interrater reliability of goniometric (GON) and trigonometric (TRIG) techniques for assessing hip-extension range of motion during the modified Thomas test. DESIGN: Controlled laboratory study. SETTING: Institutional athletic therapy facility. PATIENTS OR OTHER PARTICIPANTS: A total of 22 individuals (12 men, 10 women; age range, 18-36 years) with no pathologic knee or back conditions. MAIN OUTCOME MEASURE(S): Hip-extension range of motion of each participant during a modified Thomas test was assessed by 2 examiners with both GON and TRIG techniques in a randomly selected order on 2 separate days. RESULTS: The intraclass correlation coefficient (ICC) revealed that the reliability of the GON technique was low for both the intrarater (ICC = 0.51, 0.54) and interrater (ICC = 0.30, 0.65) comparisons, but the reliability of the TRIG technique was high for both intrarater (ICC = 0.90, 0.95) and interrater (ICC = 0.91, 0.94) comparisons. Single-factorial repeated-measures analyses of variance revealed no mean differences in scoring within or between examiners for either measurement protocol, whereas a difference was observed when comparing the TRIG and GON tests due to the differences in procedures used to identify landmarks. CONCLUSIONS: Using the TRIG technique to measure hip-extension range of motion during the modified Thomas test results in superior intrarater and interrater reliability when compared with the GON technique.

Location of a ligand recognition site of FMRFamide-gated Na(+) channels.

The second FMRFamide-gated Na(+) channel (HtFaNaC), from Helisoma trivolvis, has been cloned. HtFaNaC has some different pharmacological properties to HaFaNaC, from Helix aspersa, which has enabled a rational approach to be made to start to identify the FMRFamide recognition site. Several chimeras were made by switching sections between the channels. The differences in sensitivity to FMRFamide, and amiloride, were assessed after expression in Xenopus oocytes. The data suggest that a recognition site for FMRFamide, and the potentiating action of amiloride, resides in a sequence of about 120 amino acids in the extracellular loop proximal to the first transmembrane segment.

Baclofen exacerbates epileptic myoclonus in kindled rats.

Electrically kindled rats exhibit myoclonic jerks (1-25/min for 30-90 min) when injected with 200 mg/kg i.p. cysteamine. L-Baclofen, 10 mg/kg i.p. injected 45 min prior was not anticonvulsant but rather exacerbated the myoclonus. Furthermore, baclofen itself induced myoclonus in 29% of kindled rats at 10 mg/kg and in 100% of kindled rats at 15 mg/kg. These findings suggest that caution should be exercised before proposing the use of baclofen as an anticonvulsant or indeed using baclofen in patients who are predisposed to seizures.

Actions of baclofen on components of the Ca-current in rat and mouse DRG neurones in culture.

1. Ca currents in rat and mouse sensory dorsal root ganglion (DRG) neurones were inhibited by concentrations of (-)-baclofen as low as 1 micron. The proportion of neurones responding to baclofen was low (less than 20%), except in young cultures of neonate rat DRG neurones (3 days in culture), where 86% of the neurones were responsive. 2. Three types of unitary Ca currents were observed in the rat DRG neurones, corresponding to the T-, N- and L-type currents of chick DRG neurones. 3. Baclofen produced two types of response on whole-cell currents of DRG neurones from both species. The first was on an early inactivating component of the Ca current. This early current was partially inactivated at a holding potential of -40 mV. It was also reduced during the second of a pair of depolarizing command pulses. The results suggest that this action of baclofen is due to an action on an N-type component of the current. The second response to baclofen persisted throughout the command step and was not reduced during the second of a pair of command pulses, indicating that this effect is due to an action on the L-type current. 4. Unitary or ensemble Ca currents recorded in cell-attached patches, on neurones previously shown to respond to baclofen in whole-cell clamp mode, were generally not inhibited by baclofen application external to the patch electrode. This indicates that a readily diffusible internal second messenger substance is probably not involved in coupling the GABAB receptor to the ion channels.

Glutamic acid mimicking of synaptic inhibition on the giant serotonin neurone of the snail.

Stimulation of the snail's tentacle nerves results in hyperpolarization and inhibition of the 'giant serotonin-containing neurone'located in the brain. Glutamic acid mimics this effect. Available data indicate that the reversal potential for the glutamic acid effect is very similar to that of the synaptic action being about 5 to 8 mV more negative than the resting potential in each case.

A simple method for measuring a picogram of acetylcholine using the clam (Mya arenaria) heart.

1. A simple and reliable method is described for assaying 1 pg or less of acetylcholine (ACh) using a strip of clam (Mya arenaria) heart.2. Clam heart preparations generally are extremely selective for ACh. The preparation described is at least 10(5) times less sensitive to the following: acetyl coenzyme A, adrenaline, choline, dopamine, gamma-aminobutyric acid, glutamic acid, histamine, 5-hydroxytryptamine and noradrenaline.3. Because this preparation is one of the most sensitive known for detecting ACh, it should prove useful for assaying particularly low levels of this substance in biological extracts.

Modulation of GABAA receptor activity by alphaxalone.

The modulation of the gamma-aminobutyric acidA (GABAA) receptor by alphaxalone has been investigated by use of voltage-clamp recordings from enzymatically isolated bovine chromaffin cells maintained in cell culture. Alphaxalone (greater than 30 nM) reversibly and dose-dependently potentiated the amplitude of membrane currents elicited by locally applied GABA (100 microM). The potentiation was not associated with a change in the reversal potential of GABA-evoked currents and was not influenced by the benzodiazepine receptor antagonist, Ro15-1788 (300 nM). At relatively high concentrations (greater than 1 microM), alphaxalone directly elicited a membrane current. It is concluded that such currents result from GABAA receptor activation since they were reversibly suppressed by bicuculline (3 microM), dose-dependently enhanced by phenobarbitone (100-500 microM), and had a similar reversal potential (approximately 0 mV) to currents elicited by GABA. Additionally, on outside-out membrane patches, alphaxalone activated single channel currents with amplitudes and a reversal potential similar to those evoked by GABA. Alphaxalone (30 nM-1 microM) had no effect upon the amplitude of membrane currents elicited by locally applied acetylcholine (ACh) (100 microM). However, higher concentrations of alphaxalone (10-100 microM) reversibly suppressed ACh-evoked currents, the IC50 for blockade being 20 microM. The beta-hydroxy isomer of alphaxalone, betaxalone (100 nM-1 microM), did not potentiate GABA-induced currents, nor did higher concentrations of the steroid (10-100 microM) directly evoke a membrane current. However, over the latter concentration range, betaxalone suppressed the amplitude of currents elicited either by GABA or ACh. The relevance of the present results to the anaesthetic action of alphaxalone is discussed together with the broader implications of steroidal modulation of the GABAA receptor.

Ligand-gated ion channels opened by 5-HT in molluscan neurones.

1. 5-Hydroxytryptamine (5-HT) activated a fast (70 ms to half maximum) and desensitizing inward current through non-selective channels conducting predominantly monovalent cations in neurons of Helix aspersa. 2. alpha-Methyl-5-HT was equipotent with 5-HT in activating this current, but the known selective agonists at vertebrate 5-HT3 receptors, 2-methyl-5-HT and arylbiguanides were ineffective (< 100 microM). 5-Methoxytryptamine which is inactive on vertebrate 5-HT3 receptors was a very weak agonist. 3. The responses were antagonized by the specific vertebrate 5-HT3 receptor blocker MDL-72222 (IC50 = 1 microM), but were only weakly affected by ondansetron (10 microM). The 5-HT2-type antagonist, ketanserin (< 5 microM) had no effect. The responses were also antagonized by the non-specific antagonists (+)-tubocurarine and strychnine. 4. Unitary currents through channels non-selective for monovalent cations, and with a conductance of 2pS, could be activated repeatedly by 5-HT or alpha-methyl-5-HT in outside-out patches from neurones exhibiting the fast 5-HT-activated current (I[5-HT]fast), even in the presence of 500 microM GDP-[beta S] in the recording pipette. This strongly supports direct-gating of these channels by 5-HT. The properties of these unitary currents resembled those of I[5-HT]fast. 5. The pharmacological properties of this molluscan 5-HT-operated, ligand-gated channel differed sufficiently from known vertebrate 5-HT3-type receptors to suggest that it represents a new class of 5-HT receptor.

Functional characteristics of heteromeric Cx40-Cx43 gap junction channel formation.

Cx40:Cx43 expression ratio in A7r5 cells is augmented in growth stimulated vs. growth arrested conditions. To determine the impact of changing Cx40:Cx43 expression ratio on gap junction function, we have developed A7r5 cell lines that display Cx40:Cx43 ratios of 1:1 (66B5n) and 10:1 (A7r540C3). When Rin43 cells were paired with these coexpressing cells, there was an increasing asymmetry of voltage dependent gating as the Cx40:Cx43 ratio increased in the coexpressing cell. This asymmetry was opposite to that which is predicted by Cx40/Cx43 heterotypic channels. In addition, when Rin43 cells were paired with coexpressing cells there was a shift toward smaller single channel event amplitudes with increasing Cx40:Cx43 ratio in the coexpressing cell. Again, this is opposite to that which is predicted by Cx40/Cx43 heterotypic channels. In dye coupling experiments, 6B5N, A7r5, and A7r540C3 cells displayed charge and size selectivity that increased with increasing Cx40:Cx43 expression ratio. These data indicate that although the electrophysiological properties of heteromeric/heterotypic channels are not directly related to the proportions of Cx constituents that comprise the channel, the dye permeability data fit what would be predicted by an increase in Cx40:Cx43 ratio.

The wide range of actions of the FMRFamide-related peptides and the biological importance of peptidergic messengers.

The importance of peptides as intercellular messengers is discussed. The view is put forward that peptides evolved early in evolution as chemical messengers and that they have come to exert a wide range of actions. Using as an example the FMRFamide (Phe-Met-Arg-Phe-NH2) related peptide family of molluscs, the wide range of peptide actions on membrane currents is discussed and considered in relation to co-localization of peptides with low molecular weight (or "classical") intercellular messengers.

Actions of FMRFamide-related peptides on the gCa2+ of the C1 neuron in Helix aspersa.

The endogenous neuropeptides FMRFamide and FLRFamide (tetrapeptides) reversibly reduced a voltage-activated calcium current in the C1 neuron of Helix aspersa by an average of 20%. Two structurally related heptapeptides, pQDPFLRFamide and pQDPFLRIamide, both derived from another precursor protein in this species, did not reduce the current at all.

Biological activity and receptor binding properties of some C-terminally modified analogues of FMRFamide.

The functional role of the C-terminal amide group (-CONH2) of the molluscan regulatory peptide FMRFamide has been examined in two sets of analogues based on FnLKFamide and FnLRFamide (nL = norleucine). In each series the amide group was replaced by -CONHCH3, -CON(CH3)2, -CONHNH2, -COOCH3, -CH2OH, and -COOH. The analogues were tested for their ability to bind to receptors in membranes from Helix aspersa circumoesophageal ganglia and for their biological effects on the isolated Helix heart. The results indicate i) that agonist activity, but not binding to the receptor, requires the presence of the amide carbonyl group; ii) the hydrogen atoms of the amide group are not essential either for binding or for agonist activity (the mono- and dimethylamides were more effective than the parent compounds on both counts); iii) the is more effective an agonist than is the amide in stimulating Helix heart.

Biological activity and receptor binding properties of some analogues of pQDPFLRFamide.

To investigate the role of the N-terminal region of the heptapeptide FMRFamide-like peptide, pQDPFLRFamide, three analogues were synthesized. The analogues [pQNPFLRFamide, pQDAibFLRFamide (Aib = aminoisobutyric acid) and pQDGFLRFamide] contained modifications at amino acid residues 2 and 3, which we believed might be critical for maintaining the bioactive conformation of the heptapeptide. The analogues were tested for their ability to bind to receptors in membranes from Helix aspersa circumoesophageal ganglia and for their biological effects on the isolated Helix heart, the Helix tentacle retractor muscle, and extensor-tibiae neuromuscular preparation of the locust. Schistocerca gregaria. The substitution of Asn for Asp2 and that of Aib for Pro3 were conservative with respect to retention of heptapeptide-like biological activity, whereas the substitution of Gly for Pro3 significantly improved the binding affinity of the peptide for the FMRFamide receptors and conferred on the peptide some characteristic FMRFamide-like biological activity. Thus, pQDPFLRFamide bioactivity may depend on a bent conformation in solution.