The impact of climatic factors on tick-related hospital visits and borreliosis incidence rates in European Russia

Tick-borne diseases are among the challenges associated with warming climate. Many studies predict, and already note, expansion of ticks’ habitats to the north, bringing previously non-endemic diseases, such as borreliosis and encephalitis, to the new areas. In addition, higher temperatures accelerate phases of ticks’ development in areas where ticks have established populations. Earlier works have shown that meteorological parameters, such as temperature and humidity influence ticks’ survival and define their areas of habitat. Here, we study the link between climatic parameters and tick-related hospital visits as well as borreliosis incidence rates focusing on European Russia. We have used yearly incidence rates of borreliosis spanning a period of 20 years (1997-2016) and weekly tick-related hospital visits spanning two years (2018-2019). We identify regions in Russia characterized by similar dynamics of incidence rates and dominating tick species. For each cluster, we find a set of climatic parameters that are significantly correlated with the incidence rates, though a linear regression approach using exclusively climatic parameters to incidence prediction was less than 50% effective. On a weekly timescale, we find correlations of different climatic parameters with hospital visits. Finally, we trained two long short-term memory neural network models to project the tick-related hospital visits until the end of the century, under the RCP8.5 climate scenario, and present our findings in the evolution of the tick season length for different regions in Russia. Our results show that the regions with an expected increase in both tick season length and borreliosis incidence rates are located in the southern forested areas of European Russia. Oppositely, our projections suggest no prolongation of the tick season length in the northern areas with already established tick population.

Respiration rates of individual bovine in vitro-produced embryos measured with a novel, non-invasive and highly sensitive microsensor system

Oxygen consumption is a useful parameter for evaluating embryo quality, since it provides a valuable indication of overall metabolic activity. Over the years, several approaches have been used to measure the respiration rates of individual embryos, but a convincing method has not yet been reported. In this study, we introduce and have validated a novel high resolution microsensor technology to determine the respiration rates of individual embryos at different developmental stages. We have employed this technology to investigate the correlation between respiration rate and embryo morphology, diameter and sex. Following morphological evaluation, individual respiration rates of day 3 (n= 18) and day 7 (n= 60) bovinein vitro-produced embryos were determined. Of the measured embryos, 64 were lysed for sex diagnosis by PCR. Average respiration rates of day 7 embryos (1.30 ± 0.064 nl/h) were 3.4-fold higher than day 3 embryos (0.38 ± 0.011 nl/h). On day 7, the average respiration rate of quality 1 blastocysts was significantly higher than the respiration rates of the lower qualities. For both day 3 and day 7 embryos, respiration rates were directly influenced by embryo diameter but did not differ between sexes. These results have demonstrated that the novel microsensor technology can be used to accurately and rapidly (8 min) measure the respiration rates of individual embryos at different developmental stages. Respiration rates were only in partial agreement with embryo morphology, suggesting a slight discrepancy between these two methods in assessing embryo quality. It is likely that a combined assessment of embryo respiration and morphology would improve embryo classification and subsequent selection.

297 A CASE REPORT: THE OUTCOME OF IVP MAY BE RELATED TO THE BATCH OF TCM-199 IN IVM

Chemicals used in bovine IVP may be inhibitory to embryo development (see, e.g., Van Soom A et al. 1994 Theriogenology 41, 325). The present study continued earlier experiments to optimize serum-free IVM protocol for bovine oocytes (Räty M. 2004 Reprod. Fert. Dev. 16, 281). The embryo development rate was much lower in the new experiments than in our previous studies. Thorough testing indicated that the batch of TCM-199 medium used in maturation was the reason for the lower embryo development results. In total, 14,589 abattoir-derived bovine oocytes in 23 batches were matured for 24 h in TCM-199 with glutamax-I (GIBCO, Paisley, UK), 0.25 mM Na-pyruvate, 100 IU mL−1 penicillin, 100 μg mL−1 streptomycin, 10 μg mL−1 LH, 2 μg mL−1 FSH, and 1 μg mL−1 β-estradiol supplemented as follows: (1) 10% FBS (GIBCO, New Zealand); (2) 4 mg mL−1 fatty acid-free albumin (FAFBSA) (Sigma-Aldrich, Helsinki, Finland); (3) 4 mg mL−1 polyvinylpyrrolidone (PVP) (Sigma) + growth factors (GF; 100 ng mL−1 IGF-I + 100 ng mL−1 EGF); or (4) as (3) but without FSH, LH, and β-estradiol (PVPGFwoH). Fertilized oocytes were denuded and cultured in modified SOFaaci + 4 mg mL−1 FAFBSA in 5% O2. (Holm P. et al. 1999 Theriogenology 52, 683–700). Two TCM-199 batches were used in separate IVM runs, batch 1 (Lot#3075638; 10 runs) and batch 2 (Lot#3081334; 13 runs). The statistical analyses were based on generalized linear mixed models. The estimated probabilities for embryo cleavage and development are shown in Table 1. The use of TCM-199 batch 1 resulted in significantly lower embryo development rates than the use of TCM-199 batch 2 in every IVM group studied. PVP IVM groups were the most sensitive for the TCM-199 batch and resulted in reduced embryo cleavage as well as strikingly low Day 7 embryo development. Our results indicate that TCM-199 batch 1 disturbed embryo development. In defined IVM groups (PVP groups), the maturation inhibiting role of TCM-199 batch 1 was seen already at the cleavage stage. It is possible that FBS and FAFBSA may have protected the oocytes to some extent against inhibitory effects of TCM-199. There is evidence for BSA acting as a chelating agent (see, e.g., Flood L.P. and Shirley B. 1991 Mol. Reprod. Dev. 30, 226–231). Table 1. Estimated probability for embryo cleavage at 38–42 hpi and Day 7 embryo development after IVM in two different batches of TCM-199

2 CORRELATION BETWEEN OXYGEN RESPIRATION RATES AND MORPHOLOGY, SEX, DIAMETER AND DEVELOPMENTAL STAGE OF SINGLE BOVINE IVP-EMBRYOS

A simple, non-invasive, rapid and sensitive oxygen microsensor system was developed to investigate correlations between oxygen respiration rates of individual bovine embryos and their morphology, sex, diameter and developmental stage. Bovine IVP-embryos (n = 78; Holm et al. Theriogenology 52, 683–700) were analysed around the 8-cell stage (Day 3; n = 18) and at various blastocyst stages (Day 7; n = 60). Each embryo was morphologically evaluated, its outer diameter measured and was then loaded into a glass tube (i.d. 0.68 mm, length 3 mm). After 1 h, oxygen concentration gradients generated by the embryo’s respiration were measured over app. 8 min with an oxygen microelectrode (www.unisense.com). Five embryos were measured in one round together with an empty tube as control. The procedure was repeated twice for each embryo with app. 1 h interval. Individual respiration rates in nL O2/embryo/h (nL/h) were calculated from these gradients. The measurements were performed at 38.5°C under constant flow of humidified 5% CO2 in air (app. 19% O2). After this, 64 embryos (14 Day 3; 50 Day 7) were lysed for sex diagnosis by PCR. Values are given as mean ± SD. The sensitivity of the oxygen measurement system was high (controls: 0.034 ± 0.035 nL/h, n = 15) and its repeatability from 1st to 2nd measurement was 99.7 ± 9.8% (n = 71). The average embryo respiration rate was 0.39 ± 0.05 nLl/h on Day 3 (n = 18) and 1.31 ± 0.52 nLl/h on Day 7 (n = 60). For Day 7 embryos, the respiration rates varied according to their morphological quality, being 1.87 ± 0.46a (n = 18), 1.17 ± 0.32b (n = 23), 0.95 ± 0.27b,c (n = 14) and 0.72 ± 0.24c (n = 4) nL/h for quality 1, 2, 3, and 4 embryos, respectively (Proc Mixed,a,b,c: P < 0.05; values with different superscripts differ significantly). The sex ratio (male:female) was 9:5 (Day 3) and 32:18 (Day 7), and on Day 7 this ratio varied between qualities: 11:2, 12:8, 8:4, and 1:3 for quality 1, 2, 3, and 4, respectively. The average respiration rate on day 3 was the same for males and females, as it was on day 7 (1.22 ± 0.43 nL/h (females) and 1.31 ± 0.58 nL/h (males), P > 0.05). There was a correlation between embryo diameter and respiration rate (r2 = 0.65, n = 74), which was even stronger for Day 7 male embryos (r2 = 0.72, n = 32). In conclusion, a highly reliable, repeatable and sensitive system was established for measuring respiration rates in single bovine embryos, even at early developmental stages. The respiration rate was lower on day 3 compared to Day 7 embryos, and it was correlated with the morphological embryo quality on Day 7. Oxygen consumption could be a valuable supplementary indicator of embryo viability, especially in difficult evaluations (e.g. quality 2 and 3 after IVP). It remains to be demonstrated if such measurements can also reveal quality differences already at Day 3, which would be of interest in, e.g. the human field. ASL is supported by FCT, Portugal.

286 THE EFFECT OF IN VITRO MATURATION MEDIUM ON CRYOSURVIVAL, CELL NUMBERS AND APOPTOTIC INDEXES OF BOVINE EMBRYOS

The success of in vitro maturation (IVM) has a significant impact on the oocytes ability to develop to blastocyst stage. The quality of the produced blastocysts can be evaluated using staining techniques. The aims of this study were (a) to compare the effect of different IVM media on embryo production rates, and (b) to utilize differential (DF) and TUNEL staining to evaluate the quality and cryosurvival of the produced blastocysts. Abattoir-derived oocytes were randomly divided into the IVM groups: (1) M199 IVM (n = 2305): TCM-199 with glutamax-I (GIBCO, Paisley, UK), 0.25 mM Na-pyruvate, 100 IU mL−1 penicillin, and 100 μg mL−1 streptomycin; (2) FBS IVM (n = 2484): M199 IVM medium with hormones (10 μg mL−1 LH, 2 μg mL−1 FSH, and 100 μg mL−1 β-estradiol), and 10% FBS (GIBCO, New Zealand); and (3) FAFBSA IVM (n = 2411): as group (2), but FBS was replaced with 4 mg mL−1 fatty acid free albumin. Fertilized oocytes were denuded and cultured in modified SOFaaci + 4 mg mL−1 FAFBSA in 5% O2 (Holm P et al. 1999 Theriogenology 52, 683–700). Fresh, Grade I Day 7 blastocysts were stained with TUNEL (n = 114) or with DF (n = 149). In addition, 184 Grade I Day 7 blastocysts were frozen in AG Freeze (AB Technology, Pullman, WA, USA), thawed, and cultured for 24 h. The re-expanded embryos were stained with TUNEL (n = 96) or with DF (n = 88). Modified TUNEL protocol (Upstate, Lake Placid, NY, USA; Makarevich A and Markkula M 2002 Biol. Reprod. 66, 386–392) and DF staining protocol (Thouas G.A. et al. 2001 Reprod Biomed Online 3, 25–29) were used. The results of embryo cleavage and D7 embryo development are based on logistic regression models, and the results of proportion of ICM and apoptotic index on general linear mixed models. After FBS IVM, 83.6% of the fertilized oocytes were estimated to cleave and 25.5% to develop to the blastocyst stage by Day 7. The estimations for embryo cleavage and Day 7 development rates were significantly lower in FAFBSA IVM and M199 IVM groups (P < 0.0001): 74.0% and 15.0% for the FAFBSA, and 76.1% and 8.8% for the M199, respectively. The re-expansion rates (%) after thawing were 86.5, 90.6, and 73.3 for the FBS, FAFBSA, and M199 IVM groups, respectively. Freezing reduced the ICM proportions and elevated the apoptotic indexes (P < 0.001). The rate of ICM reduction after freezing was not influenced by the IVM medium. There was a significant interaction between the apoptotic index and the IVM group (P = 0.04). The increase of the apoptotic index was smallest in FAFBSA IVM and greatest in M199 IVM. The results indicate that exclusion of serum from IVM medium results in lower embryo cleavage and development rates. Freezing reduced ICM and increased apoptotic index of Day 7 embryos in every IVM group studied. FAFBSA IVM seemed to produce embryos of better quality as evidenced by the smallest increase in the apoptotic index after freezing.

Ratio of proliferating cell nuclear antigen-positive nuclei to total cell number is higher in day 7 than in day 8 vitrified in vitro-produced bovine embryos

The aim of the present study was to find a reliable functional criterion for the evaluation of the proliferation potential of bovine in vitro-produced embryos. We used immunocytochemical detection of proliferating cell nuclear antigen (PCNA) combined with propidium iodide (PI) staining and subsequent confocal laser scanning microscopy together with routine morphological evaluation under a stereomicroscope to study fresh Day 7, 8, and 9, and cryopreserved Day 7 and 8 embryos. The ratio of PCNA/PI-positive nuclei was equal in fresh Day 7 and Day 8 embryos and significantly lower in Day 9 embryos. In general, Day 7 embryos tolerated the cryopreservation treatments better than Day 8 embryos. Vitrification in normal straws was especially detrimental to Day 8 embryos. In fresh Day 7 and 8 embryos, the PCNA results were in agreement with stereomicroscopic evaluation. However, in Day 9 fresh and in Day 7 and 8 treated embryos, the missing PCNA revealed disorders that were not observed under morphological evaluation. PCNA immunocytochemistry is an effective method to obtain information about the functional state of nuclei. The ratio of PCNA-positive nuclei can provide more information and numerical data about the developmental potential of bovine embryos after cryopreservation.