Otoferlin acts as a Ca2+ sensor for vesicle fusion and vesicle pool replenishment at auditory hair cell ribbon synapses

Hearing relies on rapid, temporally precise, and sustained neurotransmitter release at the ribbon synapses of sensory cells, the inner hair cells (IHCs). This process requires otoferlin, a six C2-domain, Ca2+-binding transmembrane protein of synaptic vesicles. To decipher the role of otoferlin in the synaptic vesicle cycle, we produced knock-in mice (Otof Ala515,Ala517/Ala515,Ala517) with lower Ca2+-binding affinity of the C2C domain. The IHC ribbon synapse structure, synaptic Ca2+ currents, and otoferlin distribution were unaffected in these mutant mice, but auditory brainstem response wave-I amplitude was reduced. Lower Ca2+ sensitivity and delay of the fast and sustained components of synaptic exocytosis were revealed by membrane capacitance measurement upon modulations of intracellular Ca2+ concentration, by varying Ca2+ influx through voltage-gated Ca2+-channels or Ca2+ uncaging. Otoferlin thus functions as a Ca2+ sensor, setting the rates of primed vesicle fusion with the presynaptic plasma membrane and synaptic vesicle pool replenishment in the IHC active zone

Developmental Acquisition of a Rapid Calcium-Regulated Vesicle Supply Allows Sustained High Rates of Exocytosis in Auditory Hair Cells

Auditory hair cells (HCs) have the remarkable property to indefinitely sustain high rates of synaptic vesicle release during ongoing sound stimulation. The mechanisms of vesicle supply that allow such indefatigable exocytosis at the ribbon active zone remain largely unknown. To address this issue, we characterized the kinetics of vesicle recruitment and release in developing chick auditory HCs. Experiments were done using the intact chick basilar papilla from E10 (embryonic day 10) to P2 (two days post-hatch) by monitoring changes in membrane capacitance and Ca2+ currents during various voltage stimulations. Compared to immature pre-hearing HCs (E10-E12), mature post-hearing HCs (E18-P2) can steadily mobilize a larger readily releasable pool (RRP) of vesicles with faster kinetics and higher Ca2+ efficiency. As assessed by varying the inter-pulse interval of a 100 ms paired-pulse depolarization protocol, the kinetics of RRP replenishment were found much faster in mature HCs. Unlike mature HCs, exocytosis in immature HCs showed large depression during repetitive stimulations. Remarkably, when the intracellular concentration of EGTA was raised from 0.5 to 2 mM, the paired-pulse depression level remained unchanged in immature HCs but was drastically increased in mature HCs, indicating that the Ca2+ sensitivity of the vesicle replenishment process increases during maturation. Concomitantly, the immunoreactivity of the calcium sensor otoferlin and the number of ribbons at the HC plasma membrane largely increased, reaching a maximum level at E18-P2. Our results suggest that the efficient Ca2+-dependent vesicle release and supply in mature HCs essentially rely on the concomitant engagement of synaptic ribbons and otoferlin at the plasma membrane

Psychosocial work load and stress in the geriatric care

<p>Abstract</p> <p>Background</p> <p>Due to the decrease in informal care by family members and the demographic development, the importance of professional geriatric care will rise considerably. Aim of this study was to investigate the psychosocial workplace situation for employees in this profession.</p> <p>Methods</p> <p>The German version of the COPSOQ (Copenhagen Psychosocial Questionnaire) was used for the assessment of psychosocial factors at work. The instrument includes 22 scales and 3 single items concerning demands, control, stress, support, and strain.</p> <p>Results between two study groups of geriatric care were compared to each other as well as to employees in general hospital care and a general population mean (COPSOQ database).</p> <p>Statistical analysis included t-tests, ANOVA and multiple comparisons of means. Statistical significance (p < 0.01, two-tailed) and a difference of at least 5 points in mean values were defined as the relevant threshold.</p> <p>Results</p> <p>In total 889 respondents from 36 institutions took part in the study. 412 worked in Home Care (HC), 313 in Geriatric Nursing Homes (GNH), 164 in other professions (e.g. administration).</p> <p>Comparison between HC and GNH showed more favourable values for the first group for the most scales, e.g. lower quantitative and emotional demands and less work-privacy conflict, better possibilities for development etc. Compared to external values from the German COPSOQ database for general hospital care (N = 1.195) and the total mean across all professions, COPSOQ-total (N = 11.168), the results are again positive for HC workers on most of the scales concerning demands and social support. The only negative finding is the very low amount of social relations at work due to the obligation to work alone most of the time. Employees in GNH rate predictability, quality of leadership and feedback higher when compared to general hospital care and show some further favourable mean values compared to the COPSOQ mean value for all professions. A disadvantage for GNH is the high rating for job insecurity.</p> <p>A supplementary subgroup analysis showed that the degree of negative evaluation of psychosocial factors concerning demands was related to the amount of working hours per week and the number of on-call duties.</p> <p>Conclusions</p> <p>Compared to employees in general hospital care and the COPSOQ overall mean value across all professions, geriatric care employees and especially home care workers evaluate their psychosocial working situation more positive for most aspects. However, this seems partly due to the very high proportion of part-time workers. Critical results for the two study groups are the relatively high job insecurity in nursing homes and the lack of social relations for the HCrs.</p

Harvesting Electricity with Geobacter bremensis Isolated from Compost

Electrochemically active (EA) biofilms were formed on metallic dimensionally stable anode-type electrode (DSA), embedded in garden compost and polarized at +0.50 V/SCE. Analysis of 16S rRNA gene libraries revealed that biofilms were heavily enriched in Deltaproteobacteria in comparison to control biofilms formed on non-polarized electrodes, which were preferentially composed of Gammaproteobacteria and Firmicutes. Among Deltaproteobacteria, sequences affiliated with Pelobacter and Geobacter genera were identified. A bacterial consortium was cultivated, in which 25 isolates were identified as Geobacter bremensis. Pure cultures of 4 different G. bremensis isolates gave higher current densities (1400 mA/m2 on DSA, 2490 mA/m2 on graphite) than the original multi-species biofilms (in average 300 mA/m2 on DSA) and the G. bremensis DSM type strain (100–300 A/m2 on DSA; 2485 mA/m2 on graphite). FISH analysis confirmed that G. bremensis represented a minor fraction in the original EA biofilm, in which species related to Pelobacter genus were predominant. The Pelobacter type strain did not show EA capacity, which can explain the lower performance of the multi-species biofilms. These results stressed the great interest of extracting and culturing pure EA strains from wild EA biofilms to improve the current density provided by microbial anodes

Structure and mechanics of supporting cells in the guinea pig organ of Corti.

The mechanical properties of the mammalian organ of Corti determine its sensitivity to sound frequency and intensity, and the structure of supporting cells changes progressively with frequency along the cochlea. From the apex (low frequency) to the base (high frequency) of the guinea pig cochlea inner pillar cells decrease in length incrementally from 75-55 µm whilst the number of axial microtubules increases from 1,300-2,100. The respective values for outer pillar cells are 120-65 µm and 1,500-3,000. This correlates with a progressive decrease in the length of the outer hair cells from >100 µm to 20 µm. Deiters'cell bodies vary from 60-50 µm long with relatively little change in microtubule number. Their phalangeal processes reflect the lengths of outer hair cells but their microtubule numbers do not change systematically. Correlations between cell length, microtubule number and cochlear location are poor below 1 kHz. Cell stiffness was estimated from direct mechanical measurements made previously from isolated inner and outer pillar cells. We estimate that between 200 Hz and 20 kHz axial stiffness, bending stiffness and buckling limits increase, respectively,~3, 6 and 4 fold for outer pillar cells, ~2, 3 and 2.5 fold for inner pillar cells and ~7, 20 and 24 fold for the phalangeal processes of Deiters'cells. There was little change in the Deiters'cell bodies for any parameter. Compensating for effective cell length the pillar cells are likely to be considerably stiffer than Deiters'cells with buckling limits 10-40 times greater. These data show a clear relationship between cell mechanics and frequency. However, measurements from single cells alone are insufficient and they must be combined with more accurate details of how the multicellular architecture influences the mechanical properties of the whole organ

Single-Nucleotide Polymorphism Genotyping Identifies a Locally Endemic Clone of Methicillin-Resistant Staphylococcus aureus

We developed, tested, and applied a TaqMan real-time PCR assay for interrogation of three single-nucleotide polymorphisms that differentiate a clade (termed ‘t003-X’) within the radiation of methicillin-resistant Staphylococcus aureus (MRSA) ST225. The TaqMan assay achieved 98% typeability and results were fully concordant with DNA sequencing. By applying this assay to 305 ST225 isolates from an international collection, we demonstrate that clade t003-X is endemic in a single acute-care hospital in Germany at least since 2006, where it has caused a substantial proportion of infections. The strain was also detected in another hospital located 16 kilometers away. Strikingly, however, clade t003-X was not found in 62 other hospitals throughout Germany nor among isolates from other countries, and, hence, displayed a very restricted geographical distribution. Consequently, our results show that SNP-typing may be useful to identify and track MRSA clones that are specific to individual healthcare institutions. In contrast, the spatial dissemination pattern observed here had not been resolved by other typing procedures, including multilocus sequence typing (MLST), spa typing, DNA macrorestriction, and multilocus variable-number tandem repeat analysis (MLVA)

Preconceptional factors associated with very low birthweight delivery in East and West Berlin: a case control study

BACKGROUND: Very low birthweight, i.e. a birthweight < 1500 g, is among the strongest determinants of infant mortality and childhood morbidity. To develop primary prevention approaches to VLBW birth and its sequelae, information is needed on the causes of preterm birth, their personal and social antecedents, and on conditions associated with very low birthweight. Despite the growing body of evidence linking sociodemographic variables with preterm delivery, little is known as to how this may be extrapolated to the risk of very low birthweight. METHODS: In 1992, two years after the German unification, we started to recruit two cohorts of very low birthweight infants and controls in East and West Berlin for a long-term neurodevelopmental study. The present analysis was undertaken to compare potential preconceptional risk factors for very low birthweight delivery in a case-control design including 166 mothers (82 East vs. 84 West Berlin) with very low birthweight delivery and 341 control mothers (166 East vs. 175 West). RESULTS: Multivariate logistic regression analysis was used to assess the effects of various dichotomous parental covariates and their interaction with living in East or West Berlin. After backward variable selection, short maternal school education, maternal unemployment, single-room apartment, smoking, previous preterm delivery, and fetal loss emerged as significant main effect variables, together with living in West Berlin as positive effect modificator for single-mother status. CONCLUSION: Very low birthweight has been differentially associated with obstetrical history and indicators of maternal socioeconomic status in East and West Berlin. The ranking of these risk factors is under the influence of the political framework

Prevalence and predictors of 6-month exclusive breastfeeding among Canadian women: a national survey

<p>Abstract</p> <p>Background</p> <p>In spite of the evidence supporting the importance of breastfeeding during the first year of life, data on breastfeeding practices remain limited in Canada. The study aimed to examine the prevalence and predictors of 6-month exclusive breastfeeding among Canadian women.</p> <p>Methods</p> <p>The analysis was based on the Maternity Experience Survey targeting women aged ≥ 15 years who had singleton live births between February 2006 - May 2006 in the Canadian provinces and November 2005 - February 2006 in the territories. The main outcome was exclusive breastfeeding based on the World Health Organization definition. Socioeconomic, demographic, maternal, pregnancy and delivery related variables were considered for a multivariate logistic regression using stepwise modeling. Bootstrapping was performed to account for the complex sampling design.</p> <p>Results</p> <p>The sample size in this study was 5,615 weighted to represent 66,810 Canadian women. While ever breastfeeding was 90.3%, the 6-month exclusive breastfeeding rate was 13.8%. Based on the regression model, having higher years of education, residing in the Northern territories and Western provinces, living with a partner, having had previous pregnancies, having lower pre-pregnancy body mass index and giving birth at older age were associated with increased likelihood of 6-month exclusive breastfeeding. Moreover, smoking during pregnancy, Caesarean birth, infant's admission to the intensive care unit and maternal employment status before 6 months of infant's age were negatively associated with exclusive breastfeeding. Mothers choosing to deliver at home were more likely to remain exclusively breastfeeding for 6 months (Odds Ratio: 5.29, 95% Confidence Interval: 2.95-9.46).</p> <p>Conclusions</p> <p>The 6-month exclusive breastfeeding rate is low in Canada. The study results constitute the basis for designing interventions that aim to bridge the gap between the current practices of breastfeeding and the World Health Organization recommendation.</p