Human oocyte-derived sperm chemoattractant is a hydrophobic molecule associated with a carrier protein

Objective: To characterize the nature of the human oocyte-derived chemoattractant. Design: Laboratory in-vitro study. Setting: Academic research institute. Patients: Ten healthy sperm donors. Oocyte-conditioned media from women undergoing IVF treatment due to male factor infertility. Interventions: Sperm samples were processed by the migration–sedimentation technique. Oocyte-conditioned media were collected 2-3 h after oocyte stripping. Main Outcome Measure(s): Sperm chemotaxis was assayed in a µ-slide chamber according to the direction of swimming relative to that of the chemical gradient. Results: Oocyte-conditioned media treated with proteases did not lose their chemotactic activity; on the contrary, they became more active, with the activity shifted to lower concentrations. When oocyte-conditioned media were subjected to hexane extraction, chemotactic activity was found in both the hydrophobic and aqueous phases. Known mammalian sperm chemoattractants were ruled out as oocyte-derived chemoattractants. Conclusions: Our results suggest that the oocyte-derived chemoattractant is a hydrophobic non-peptide molecule which, in an oocyte-conditioned medium, is associated with a carrier protein that enables its presence in a hydrophilic environment

The transition to clinical expert: Enhanced decision making for children aged less than 5years attending the paediatric ED with acute respiratory conditions

© Published by the BMJ Publishing Group Limited. Background Rates of unplanned paediatric admissions are persistently high. Many admissions are short-stay events, lasting less than 48 hours. Objective This qualitative research explores factors that influence clinical decision making in the paediatric ED (PED) for children under 5 attending with acute respiratory conditions, focusing on how management decisions adapt with increasing experience. Method Semi-structured interviews were conducted with 15 PED clinicians (doctors, emergency nurse practitioners and registered nurses) with varying levels of experience in paediatric emergency medicine (PEM), emergency medicine or paediatrics. Audio-recorded interviews were transcribed and analysed thematically. Results There were clear differences in decision-making approaches between experienced clinicians and junior staff. The latter were more risk adverse, relying heavily on guidelines, set admission criteria, clinical theory and second opinions. This was particularly true for doctors. 'Informal' learning was apparent in accounts from less-experienced doctors and nurses, whereby tacit knowledge and risk management played an increasing role in the development of clinical intuition that permitted rapid assessment and treatment of young patients. Conclusions The emergence of intuition entwined with approaches to risk management and the role of these skills in clinical decision making, carry implications for the development of training programmes for clinicians working in PEM. Enhanced training for such groups to permit development of the supplementary skills described in this study could have the ability to improve care delivery and even reduce paediatric admissions

Testing Human Sperm Chemotaxis: How to Detect Biased Motion in Population Assays

Biased motion of motile cells in a concentration gradient of a chemoattractant is frequently studied on the population level. This approach has been particularly employed in human sperm chemotactic assays, where the fraction of responsive cells is low and detection of biased motion depends on subtle differences. In these assays, statistical measures such as population odds ratios of swimming directions can be employed to infer chemotactic performance. Here, we report on an improved method to assess statistical significance of experimentally determined odds ratios and discuss the strong impact of data correlations that arise from the directional persistence of sperm swimming

Behavioral Mechanism during Human Sperm Chemotaxis: Involvement of Hyperactivation

When mammalian spermatozoa become capacitated they acquire, among other activities, chemotactic responsiveness and the ability to exhibit occasional events of hyperactivated motility—a vigorous motility type with large amplitudes of head displacement. Although a number of roles have been proposed for this type of motility, its function is still obscure. Here we provide evidence suggesting that hyperactivation is part of the chemotactic response. By analyzing tracks of spermatozoa swimming in a spatial chemoattractant gradient we demonstrate that, in such a gradient, the level of hyperactivation events is significantly lower than in proper controls. This suggests that upon sensing an increase in the chemoattractant concentration capacitated cells repress their hyperactivation events and thus maintain their course of swimming toward the chemoattractant. Furthermore, in response to a temporal concentration jump achieved by photorelease of the chemoattractant progesterone from its caged form, the responsive cells exhibited a delayed turn, often accompanied by hyperactivation events or an even more intense response in the form of flagellar arrest. This study suggests that the function of hyperactivation is to cause a rather sharp turn during the chemotactic response of capacitated cells so as to assist them to reorient according to the chemoattractant gradient. On the basis of these results a model for the behavior of spermatozoa responding to a spatial chemoattractant gradient is proposed

Temporary Tasks Assignment Resolved

Among all basic on-line load balancing problems, the only unresolved problem was load balancing of temporary tasks on unrelated machines. This open problem exists for almost a decade, see [Borodin El-Yaniv]. We resolve this problem by providing an unapproximability result. In addition, a newer open question is to identify the dependency of the competitive ratio on the durations of jobs in the case where durations are known. We resolve this problem by characterizing this dependency. Finally, we provide a PTAS for the o-line problem with a xed number of machines and show a 2 unapproximability for the general case

Human oocyte-derived sperm chemoattractant is a hydrophobic molecule associated with a carrier protein

Objective: To characterize the nature of the human oocyte-derived chemoattractant. Design: Laboratory in vitro study. Setting: Academic research institute. Patient(s): Ten healthy sperm donors. Oocyte-conditioned media from women undergoing IVF treatment because of male factor infertility. Intervention(s): Sperm samples were processed by the migration-sedimentation technique. Oocyte-conditioned media were collected 2-3 hours after oocyte stripping. Main Outcome Measure(s): Sperm chemotaxis was assayed in a m-slide chamber according to the direction of swimming relative to that of the chemical gradient. Result(s): Oocyte-conditioned media treated with proteases did not lose their chemotactic activity; on the contrary, they became more active, with the activity shifted to lower concentrations. When oocyte-conditioned media were subjected to hexane extraction, chemotactic activity was found in both the hydrophobic and aqueous phases. Known mammalian sperm chemoattractants were ruled out as oocyte-derived chemoattractants. Conclusion(s): Our results suggest that the oocyte-derived chemoattractant is a hydrophobic nonpeptide molecule that, in an oocyte-conditioned medium, is associated with a carrier protein that enables its presence in a hydrophilic environment. (Fertil Steril Ò 2014;102: 885-90

Directional persistence of sperm swimming paths prompts adapted statistical test for motion bias.

<p><b>A.</b> One out of 30,000 control human sperm tracks (blue) and the corresponding averaged swimming path (purple; computed using a second-order Savitzky-Golay filter). The fast wiggling of the sperm head center is clearly visible. For later odds ratio calculations, angles ψ between a preferred direction and the frame-to-frame displacement vectors were binned according to the color wheel shown; the color-coded track illustrates the binning. <b>B.</b> Orientational correlation function <i>C</i>(<i>t</i>) of the swimming direction angle ψ for the sperm track from panel A (solid blue). This correlation function shows fast oscillations resulting from periodic head wiggling as well as slow decay on a time-scale of several seconds, which reflects directional persistence of sperm swimming. Also shown is a sample average of this autocorrelation (dotted blue) computed by averaging individual angle autocorrelation functions from <i>n</i> = 4,000 long sperm tracks (duration >10 sec). We can further define an analogous angle autocorrelation function for the direction angle of the averaged path (solid purple: for the averaged path from panel A; dotted purple: sample average). <b>C.</b> Empirical significance thresholds for the odds ratio of swimming direction angles for a human sperm population assay: An odds ratio O.R. = (<i>N</i>₊/<i>N</i>₋)/(<i>N</i>₊⁰/<i>N</i>₋⁰) greater than 1+Δ_95%(<i>N</i>) with sample size <i>N</i> = min(<i>N</i>₊+<i>N</i>₋,<i>N</i>₊⁰+<i>N</i>₋⁰) should be statistically significant for positive chemotaxis at a 5%-confidence level. The test for negative chemotaxis reads O.R.<1−Δ_5%. Significance thresholds were determined by block bootstrapping based on a large control data set of swimming direction angles of 30,000 sperm tracks. For various sample sizes <i>N</i>, we sampled a distribution of odds ratios by computing odds values for suitable random subsamples of size about <i>N</i>. Each subsample comprises the full angle data corresponding to a random selection of tracks. <i>Upper inset</i>: Distribution of odds ratios for <i>N</i> = 10⁶ by bootstrapping. The 5% and 95% percentiles of this distribution represent the significance thresholds 1−Δ_5% and 1+Δ_95%, respectively. <i>Lower inset</i>: Significance thresholds Δ*_5% and Δ*_95% for a simulated control data set devoid of correlations as a function of test sample size <i>N</i>* (continuous lines, green Δ*_5%, red Δ*_95%). We obtain almost identical “significance thresholds”, if we employ simple bootstrapping drawing subsamples from <i>pooled</i> experimental angle data (not shown). The significance thresholds determined by block bootstrapping (open symbols, green Δ_5%, red Δ_95%) superpose with those for the simulated control data if we renormalize sample size as <i>N</i>* = 0.029<i>N</i>, <i>i.e.</i> Δ*_5%(<i>N</i>*) ≈Δ_5%(<i>N</i>) and Δ*_95%(<i>N</i>*)≈Δ_95%(<i>N</i>). <i>N</i>* can be regarded as an effective number of independent data points in an experimental sample of size <i>N</i>. <b>D.</b> Odds ratios characterizing biased motion of human sperm cells in a concentration gradient of the chemoattractant progesterone for various initial concentrations (black dots). Errorbars denote symmetric 90%-confidence intervals that were determined using bootstrapping based on the data from this particular experiment. Using bootstrapping on a separate, very large control data set, we can assign accurate significance levels <i>p</i> to each odds ratio. These significance levels represent the likelihood that the odds ratios in this particular experiment were drawn from the control distribution.</p