The influence of gamete co-incubation length on the in vitro fertility and sex ratio of bovine bulls with different penetration speed

Reproductive outcomes predicted by phase imaging with computational specificity of spermatozoon ultrastructure

The ability to evaluate sperm at the microscopic level, at high-throughput, would be useful for assisted reproductive technologies (ARTs), as it can allow specific selection of sperm cells for in vitro fertilization (IVF). The tradeoff between intrinsic imaging and external contrast agents is particularly acute in reproductive medicine. The use of fluorescence labels has enabled new cell-sorting strategies and given new insights into developmental biology. Nevertheless, using extrinsic contrast agents is often too invasive for routine clinical operation. Raising questions about cell viability, especially for single-cell selection, clinicians prefer intrinsic contrast in the form of phase-contrast, differential-interference contrast, or Hoffman modulation contrast. While such instruments are nondestructive, the resulting image suffers from a lack of specificity. In this work, we provide a template to circumvent the tradeoff between cell viability and specificity by combining high-sensitivity phase imaging with deep learning. In order to introduce specificity to label-free images, we trained a deep-convolutional neural network to perform semantic segmentation on quantitative phase maps. This approach, a form of phase imaging with computational specificity (PICS), allowed us to efficiently analyze thousands of sperm cells and identify correlations between dry-mass content and artificial-reproduction outcomes. Specifically, we found that the dry-mass content ratios between the head, midpiece, and tail of the cells can predict the percentages of success for zygote cleavage and embryo blastocyst formation.

SLIM microscopy allows for visualization of DNA-containing liposomes designed for sperm-mediated gene transfer in cattle

Naked DNA has been shown to bind naturally to the sperm, a method called sperm-mediated gene transfer (SMGT). Based on these observations, we examined the efficiency of exogenous DNA binding to sperm using liposomes. In this experiment, we analyzed methods to select frozen-thawed bovine sperm, and evaluated the binding of exogenous DNA to those sperm. To determine the optimal selection method, we used Computer-Assisted Sperm Analysis (CASA). Percoll or Swim-Up were used to select sperm, followed by incubation up to 3 h with the liposome-DNA complexes. The samples were collected after 1 h and after 3 h. We used enhanced green fluorescent protein (eGFP) in combination with the liposomes as a marker for exogenous DNA binding. Five treatments per selection method were analyzed: (1) no incubation, no liposomes and no DNA, (2) incubation with no liposomes and no DNA, (3) incubation with liposomes and no DNA, (4) incubation with liposomes and 1 µg of DNA and (5) incubation with liposomes and 10 µg of DNA. The CASA results for total motility and rapid motility were statistically significant (P < 0.01) between the control and the other treatments in the Percoll group as opposed to Swim-Up. Swim-Up was therefore chosen as the optimal selection method. In order to determine if the liposome-DNA complex had bound to sperm, real time PCR was used to detect GFP DNA and images of the sperm were analyzed using the Spatial Light Interference Microscopy (SLIM). SLIM confirmed the presence of liposomes on the sperm head and tail.

Non-invasive nuclear magnetic resonance analysis of male and female embryo metabolites during in vitro embryo culture

INTRODUCTION

In the past 20+ years, several studies of bovine embryo production showed how the ratio of male to female embryos changes if embryos are made in vivo or in vitro. It is known that in in vitro systems, the sex ratio is in favor of males when there are high levels of glucose, and favors females when the principal energetic substrate is one other than glucose, like citrate.

OBJECTIVES

The aim of this study was to evaluate the embryo metabolism during three important periods of in vitro development: the early development (from day 1 until day 3), the middle of culture (day 3 until day 5), and later development (day 5 until day 7).

METHODS

To obtain this information we evaluated the spent medium from each time period by ¹H NMR.

RESULTS

Our results confirm that embryo metabolism is different between sexes. The new information obtained by identifies markers that we can use to predict the embryo sex.

CONCLUSION

These results open a new, non-invasive method to evaluate sex of the embryos before the transfer. In the first period of embryo culture, valine concentration is good indicator (66.7% accurate), while in the last phase of culture, pyruvate depletion is the best marker (64% accurate) to evaluate the sex of the embryo.

Oxidative stress differentially impacts male and female bovine embryos depending on the culture medium and the stress condition

Male and female embryos are known to differ for their metabolism and response to environmental factors very early in development. The present study aimed to evaluate the response to oxidative stress of male and female bovine embryos at the morula-blastocyst stages in terms of developmental rates, total cell number and apoptotic rates in two culture conditions. Embryos where cultured in a medium supplemented with either 5% fetal calf serum (FCS) or 4 mg/mL bovine serum albumin and a mixture of insulin, transferrin and selenium (BSA-ITS). Oxidative stress was applied at Day-5 post insemination (pi) by adding either AAPH or menadione to the culture medium, and blastocysts were analyzed at Day-7pi. The impact on development and blastocyst quality was dependent on the culture medium and the stress inducer but differed between male and female embryos. Male embryos resisted better to oxidative stress in FCS supplemented medium, no matter the stress inducer. Accordingly, the impact on blastocyst cell number tended to be higher in female blastocysts after stress induction with AAPH in FCS supplemented medium. On the other hand, in BSA-ITS supplemented medium, female embryos were more resistant to AAPH induced stress, while menadione had no impact on sex ratio. The weaker resistance of males to AAPH in this medium is in accordance with their trend to show a higher increase in apoptotic rates than females in this condition. In conclusion, this study shows that oxidative stress has differential impact on male and female bovine blastocysts depending on the culture condition and on the way oxidative stress is induced.

On the estimation of heat-intensity and heat-duration effects in time series models of temperature-related mortality in Stockholm, Sweden

BACKGROUND

We examine the effect of heat waves on mortality, over and above what would be predicted on the basis of temperature alone.

METHODS

Present modeling approaches may not fully capture extra effects relating to heat wave duration, possibly because the mechanisms of action and the population at risk are different under more extreme conditions. Modeling such extra effects can be achieved using the commonly left-out effect-modification between the lags of temperature in distributed lag models.

RESULTS

Using data from Stockholm, Sweden, and a variety of modeling approaches, we found that heat wave effects amount to a stable and statistically significant 8.1-11.6% increase in excess deaths per heat wave day. The effects explicitly relating to heat wave duration (2.0-3.9% excess deaths per day) were more sensitive to the degrees of freedom allowed for in the overall temperature-mortality relationship. However, allowing for a very large number of degrees of freedom indicated over-fitting the overall temperature-mortality relationship.

CONCLUSIONS

Modeling additional heat wave effects, e.g. between lag effect-modification, can give a better description of the effects from extreme temperatures, particularly in the non-elderly population. We speculate that it is biologically plausible to differentiate effects from heat and heat wave duration.

Effect of energy source during culture on in vitro embryo development, resistance to cryopreservation and sex ratio

The aim of this work was to evaluate whether minimizing the glucose concentration during culture or replacing the hexose with other energy substrates and/or embryotrophic compounds would affect the in vitro development, the resistance to cryopreservation and the sex ratio of bovine embryos. In vitro matured and fertilized oocytes were randomly assigned to 4 groups for in vitro culture, that differed in the energy substrates included: group A) 1.5 mM glucose, as in standard SOF; group B) 0.15 mM glucose; group C) 0.125 mM G3P, in the presence of 0.15 mM glucose and group D) 0.34 mM citrate, in combination with 2.77 mM myo-inositol. Blastocysts were evaluated on day 7, then vitrified by cryotop in 16.5% DMSO, 16.5% EG and 0.5 M sucrose and warmed in decreasing concentration of sucrose (0.25 to 0.15 M sucrose). The survival rates were assessed after 24 h in vitro culture. Finally, the blastocysts produced were sexed by PCR. An increased blastocyst rate was recorded in groups B, C and D, i.e., when glucose concentration was reduced, compared to group A (28.2, 41.0, 35.7 and 35.8, respectively in groups A, B, C and D; P < 0.01). However, the embryos cultured in group D showed the slowest developmental speed, indicated by the lowest percentage of advanced stage-embryos (expanded and hatched blastocysts) out of the total blastocysts (56.1, 45.8, 56.9 and 31.8 %, respectively in groups A, B, C and D; P < 0.01). Furthermore, survival rates after 24 h culture of vitrified-warmed blastocysts also decreased in group D (73.3, 73.1, 71.4 and 58.4%, respectively in groups A, B, C and D; P < 0.01). Interestingly, in group D a higher percentage of female embryos was obtained compared to group A, with intermediate values in groups B and C (45.6, 53.4, 50.0 and 61.5%, respectively in groups A, B, C and D; P < 0.05). In conclusion, it was demonstrated that the energy substrate during in vitro culture affects both the production and the viability of blastocysts. Furthermore, manipulating the metabolic profile of embryos during in vitro culture may have an impact on sex ratio.