Synaptic vesicle dynamics in the mossy fiber-CA3 presynaptic terminals of mouse hippocampus

The mossy fiber (MF)-CA3 synapse in the hippocampus is unique in the CNS because of its wide dynamic range of transmitter release during short- and long-term plasticity. The presynaptic mechanisms underlying the fidelity of transmission were investigated for the MF-CA3 synapses. The relative size of readily releasable pool (RRP) of vesicles was estimated by counting the number of docked vesicles at an active zone (AZ) on the transmission electron microscopy (TEM) image. The size of the releasable pool and the exo-endocytosis kinetics were directly measured from individual large MF boutons in hippocampal slices of transgenic mice that selectively express synaptopHluorin (SpH), a pH-sensitive GFP fused to the lumenal aspect of one of the vesicular membrane proteins, VAMP-2, in these boutons. Here we found (1) there are distinct two vesicle pools, the resting pool which is resistant to exocytosis, and the releasable pool, (2) the initially docked vesicles are easily depleted and the RRP is maintained by refilling from the reserve subpopulation of releasable pool ("reserve" releasable pool), and (3) the contribution of rapid reuse of recycled vesicles is relatively small. Therefore, the fidelity of transmission is suggested to be ensured by the rapid refilling rate of RRP.     

Approach of Pavement Surface Layer Degradation Caused by Tire Contact Using Semi-Analytical Model

New methods of degradations on the pavement’s surface, such as top-down cracking and delamination, caused by the repeated passage of heavy vehicles led to questions about the impact of the contact between the tire and the pavement. In fact, to increase the service life of the structures, future road design methods must have a precise knowledge of the consequences of the contact parameters on the state of stress and deformation in the pavement. In this paper, tractive rolling contact under the effect of friction is modeled by Kalker’s theory using a semi-analytical method (SAM). A tire profile is performed thanks to a digitization by fringes or a photogrammetry technique. The effect of rolling on the main surface extension deformations is then highlighted to study top cracking. At the end of the SAM calculation, contact areas are closed to 200 μdef, exceeding the allowable micro-deformation limit for the initiation of cracking. In addition, results on the main strain directions also give information on the direction of cracking (initiation of longitudinal or transverse cracks). The cracking then becomes evident, leading to a reduced service life.     

Pharmacological dissection of calcium channel subtype-related components of strontium inflow in large mossy fiber boutons of mouse hippocampus

Several subtypes of voltage-dependent calcium channels (VDCCs) are present in the presynaptic terminals. In the mammalian hippocampus, P/Q-, N-, and R- but not L-type VDCCs are involved in the fast transmitter release from large mossy fiber (MF) boutons, which are associated with CA3 pyramidal cell dendrites. We investigated whether L-type VDCCs are indeed absent in these large MF boutons. With the use of Sr2+ as the Ca2+ substitute, the stimulus-evoked Sr2+ increment (delta[Sr2+]pre) was evaluated fluorometrically. Delta[Sr2+]pre appeared to be proportional to Sr2+ inflow through VDCCs and was specifically attenuated by conventional VDCC subtype-selective antagonists. The P/Q-type selective omega-agatoxin IVA (AgTx(IVA)) blocked delta[Sr2+]pre with an IC50 of 28 nM and by 30-35% at its maximum effective concentration of 0.5 microM. The N-type selective omega-conotoxin GVIA (CgTx(GVIA)) blocked delta[Sr2+]pre with an IC50 of 15 nM and by 20-25% at its maximum effective concentration of 1 microM. The R-type selective SNX-482 blocked delta[Sr2+]pre with an IC50 of 79 nM and by 20-25% at its maximum effective concentration of 1 microM. The effects of these toxins did not overlap at their maximum effective concentrations and about 70-80% of delta[Sr +]pre was blocked by the simultaneous exposure to these toxins. delta[Sr2+]pre component that is resistant to AgTx(IVA), CgTx(IVA), and SNX-482 was significantly potentiated by an L-type agonist, (S)-(-)-Bay K8644, and attenuated by an L-type antagonist, nimodipine, suggesting that L-type VDCCs are present in large MF terminals. The L-type agonist, (+/-)-Bay K8644, also potentiated Sr2+ inflow into individual boutons identified as large MF boutons under confocal microscopy. Almost similar results were observed for Ca2+ inflow-dependent fluorescence increments. L-type VDCCs appear to be present in large MF boutons and mediate a substantial Ca2+ inflow into presynaptic terminals during action potentials.     

Profil étiologique et évolutif de l’insuffisance rénale de l’enfant en milieu hospitalier au Togo

ObjectiveTo determine the etiological and evolutionary profile of renal failure of chidren in Togo.MethodsThis is a cross-sectional study over the period of 12 months (2016–2017) including children aged 1 to 18 years hospitalized in the pediatric ward of Sylvanus Olympio university teaching hospital of Lome (Togo) for renal failure.ResultsOf 2374 patients hospitalized in our unit, 58 (2.4%) had renal failure. The mean age was 8.17 ± 4 years with a sex ratio of 1.32. The average consultation time was 11.9 days. The mean duration of hospitalization was 12.7 ± 7.7 days. Thirty-seven patients (63.8%) were referred from a peripheral center. Thirty-seven children out of 58 (63.1%) were oligoanuric. Renal failure was acute in 94.8% and chronic in 5.2%. Anemia was found in 84.4% of children. The main etiologies found were severe malaria (63.8%), glomerulonephritis (10.3%) and nephrotic syndrome (10.3%). Thirteen children (22.4%) benefited from dialysis sessions. The evolution was favorable in 79.3% of the cases.ConclusionThe renal failure of child is relatively common in our daily practice. The low socio-economic level and the lack of adapted equipment make the care difficult.     

Vitamin C levels in a Central‐African mother–infant cohort: Does hypovitaminosis C increase the risk of enteric infections?

In the MITICA (Mother‐to‐Infant TransmIssion of microbiota in Central‐Africa) study, 48 mothers and their 50 infants were followed from delivery to 6 months between December 2017 and June 2019 in Bangui (Central‐African Republic). Blood tests and stool analyses were performed in mothers at delivery, and their offspring at birth, 11 weeks and 25 weeks. Stool cultures were performed in specific growth media for Salmonella, Shigella, E. coli, Campylobacter, Enerobacter, Vibrio cholerae, Citrobacter and Klebsiella, as well as rotavirus, yeasts and parasitological exams. The median vitamin C levels in mothers at delivery were 15.3 μmol/L (inter‐quartile‐range [IQR] 6.2–27.8 μmol/L). In infants, the median vitamin C levels at birth were 35.2 μmol/L (IQR 16.5–63.9 μmol/L). At 11 and 25 weeks, the median vitamin C levels were 41.5 μmol/L (IQR 18.7–71.6 μmol/L) and 18.2 μmol/L (IQR 2.3–46.6 μmol/L), respectively. Hypovitaminosis C was defined as seric vitamin C levels <28 μmol/L and vitamin C deficiency was defined as vitamin C levels <11 μmol/L according to the WHO definition. In mothers, the prevalence of hypovitaminosis‐C and vitamin C deficiency at delivery was 34/45 (75.6%) and 19/45 (42.2%), respectively. In infants, the prevalence of hypovitaminosis‐C and vitamin C deficiency at 6 months was 18/33 (54.6%) and 11/33 (33.3%), respectively. Vitamin C levels in mothers and infants were correlated at birth (Spearman''s rho = 0.5; P value = 0.002), and infants had significantly higher levels of vitamin C (median = 35.2 μmol/L; IQR 16.5–63.9 μmol/L), compared to mothers (median = 15.3 μmol/L; IQR 6.2–27.8 μmol/L; P value <0.001). The offspring of vitamin C‐deficient mothers had significantly lower vitamin C levels at delivery (median = 18.7 μmol/L; IQR 13.3–30.7 μmol/L), compared to the offspring of non‐deficient mothers (median = 62.2 μmol/L; IQR 34.6–89.2 μmol/L; P value <0.001). Infants with hypovitaminosis‐C were at significantly higher risk of having a positive stool culture during the first 6 months of life (adjusted OR = 5.3, 95% CI 1.1; 26.1; P value = 0.038).     

Restoration of visual response in aged dystrophic RCS rats using AAV-mediated channelopsin-2 gene transfer

PURPOSE: To investigate whether the channelopsin-2 (Chop2) gene would restore visual responses in 10-month-old dystrophic Royal College of Surgeons (aged RCS; rdy/rdy) rats, the authors transferred the Chop2 gene into the retinal cells of aged RCS rats using the adenoassociated virus (AAV) vector. METHODS: The N-terminal fragment (residues 1-315) of Chop2 was fused to a fluorescent protein, Venus, in frame at the end of the Chop2 coding fragment. The viral vector construct (AAV-Chop2V) for the expression of the Chop2V in the retina was made by subcloning into an adenoassociated virus vector, including the CAG promoter. To evaluate the expression profile of Chop2V in the retina, the rats were killed and the eyes were removed and fixed with 4% paraformaldehyde in 0.1 M phosphate-buffered saline. Retinal wholemount specimens and cryosections were made. Under anesthetized conditions, electrodes for the recording of visually evoked potentials (VEPs) were implanted onto the visual cortex in aged-RCS (rdy/rdy) rats. AAV-Chop2V vectors were then injected into the vitreous cavity of the left eyes. As a control, AAV-Venus vectors were applied to the right eyes. VEPs were evoked by the flash of a blue, white, or red light-emitting diode (LED) and were recorded from the visual cortex of the rats at various time points after the AAV vector injection. RESULTS: Chop2V fluorescence was predominantly observed in retinal ganglion cells (RGCs). Some fluorescence was observed in the inner nuclear layer and the inner plexiform layer neurites. A tendency of recovery was observed in the VEPs of aged RCS (rdy/rdy) rats after the AAV-Chop2V injection but not after the AAV-Venus injection. The visual response of AAV-Chop2V-injected aged RCS (rdy/rdy) rats was less sensitive to the blue LED flash than that of nondystrophic RCS (+/+) rats. The AAV-Chop2V-injected aged RCS (rdy/rdy) rats were insensitive to the red LED flash, which evoked a robust VEP in the RCS (+/+) rats. CONCLUSIONS: The visual response of aged RCS (rdy/rdy) rats was partially restored by transduction of the Chop2 gene through AAV into the inner retinal neurons, mainly RGCs. These results suggest that the transduction of Chop2 would provide a new strategy to treat some retinitis pigmentosa (RP) symptoms independent of their etiology.     

Diabetes mellitus in children in Lomé (Togo)

AIM: Describe clinical aspects and outcome of children with diabetes mellitus in Lomé (Togo). METHODS: This work concern eighteen children consecutively admitted between 1997 and 2004 for diabetes mellitus. Diagnosis of type 2 diabetes mellitus (T2DM) were done on the presentation of at least one of T2DM risk factors: obesity, familial history of T2DM, acanthosis nigricans, polycystic ovary syndrome, dislipidemia, high blood pressure. RESULTS: Twelve children presented type 1 diabetes mellitus (T1DM), 5 T2DM and one, corticosteroids induced diabetes. At least one of the first degree parent suffered from diabetes in 4 of the 5 children with T2DM and 4 of the 12 patients with T1DM. Most patients (with T1DM or T2DM) presented polyuria, polydypsia and ketonuria at admission. All patients with T2DM were obese and had lifestyles characterised by high fat intake, sedentary attitudes, and physical inactivity. The corticosteroid induced diabetes cessed when corticosteroid stopped. The other patients were successfully treated with insulin (T1DM) or insulin then exercises and diets (T2DM). CONCLUSION: Clinical presentation of diabetes mellitus is now characterised in Togo by the emergence of T2DM which principal risks factors are obesity and familial history of T2DM.     

β-Phorbol ester-induced enhancement of exocytosis in large mossy fiber boutons of mouse hippocampus

β-Phorbol esters (BPE), synthetic analogues of diacylglycerol (DAG), induce the potentiation of transmission in many kinds of synapses through activating the C₁ domain-containing receptors. However, their effects on synaptic vesicle exocytosis have not yet been investigated. Here, we evaluated the vesicular exocytosis directly from individual large mossy fiber boutons (LMFBs) in hippocampal slices from transgenic mice that selectively express synaptopHluorin (SpH). We found that the activity-dependent increment of SpH fluorescence (ΔSpH) was enhanced by 4β-phorbol 12,13-diacetate (PDAc), one of the BPEs, without influencing the recycled component of SpH. These PDAc effects on ΔSpH were almost completely inhibited by staurosporine, a non-selective antagonist of protein kinases. However, intermittent synaptic transmission was still potentiated through a staurosporine-resistant mechanism. The staurosporine-sensitive cascade may facilitate the vesicle replenishment, thus maintaining the fidelity of transmission at a high level during repetitive firing of the presynaptic neuron. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Caring for a loved one with cancer: it is my job

This study investigated the experiences of caregivers of loved ones with cancer in Lomé, Togo. The authors developed a framework that captures the experiences of 17 caregivers. The framework explains the exploratory factors that influenced the lives of caregivers from the caregivers' own perspectives. Findings showed that even though the caregivers experienced significant challenges that affected their lives and the lives of their families, because of cultural norms and expectations, they tried their best to overcome the challenges. Although some reported positive impacts on their family functioning, others reported negative impacts such as fragmentation of the family unit. Implications for practice and policy are discussed.