Inhibition of bovine sperm-zona binding by bovine herpesvirus-1.

The purpose of the present study was to identify a potential interference of bovine herpesvirus-1 (BoHV-1) with sperm-oocyte interactions during bovine in vitro fertilization. An inhibition of almost 70% of sperm-zona binding was observed when bovine cumulus-denuded oocytes were inseminated in the presence of 10(7) 50% tissue culture infective dose/ml BoHV-1. The inhibitory effect of BoHV-1 on sperm-zona binding was mediated by an interaction of the virus with spermatozoa, but not with oocytes. Treatment of spermatozoa with BoHV-1, however, did not affect sperm motility and acrosomal status. Antiserum against BoHV-1 prevented the virus-induced inhibition of sperm-zona binding, indicating that BoHV-1 itself affects the fertilization process. In order to investigate which BoHV-1 glycoprotein(s) are responsible for the virus-sperm interaction, BoHV-1 was treated with monoclonal antibodies against the viral glycoproteins gB, gC, gD and gH prior to insemination. Anti-gC completely prevented the inhibitory effect of BoHV-1 on sperm-zona binding, while anti-gD caused a reduction of this inhibition. Further evidence for the involvement of gC and gD in the virus-sperm interaction was provided by the fact that purified gC and gD decreased sperm-zona binding in a dose-dependent way with gC being more effective than gD. These results indicated that BoHV-1 inhibits bovine sperm-zona binding by interacting with spermatozoa. The binding of BoHV-1 to a spermatozoon is mediated by the viral glycoproteins gC and gD, and therefore seems to be comparable with the mechanisms of BoHV-1 attachment to its natural host cell.

Silicone oil used in microdrop culture can affect bovine embryonic development and freezability.

The effect of silicone and paraffin oil, which is routinely used to overlay in vitro embryo culture media, on bovine in vitro embryonic development and on their subsequent survival after one-step vitrification was investigated. In experiment 1, silicone oil batch 13 was compared with paraffin oil. Embryonic development to the eight-cell and blastocyst stage was significantly impaired by silicone oil batch 13 in comparison with paraffin oil (p < 0.0001). Normal looking blastocysts produced under both types of oil were vitrified. None of the blastocysts that were produced under silicone oil batch 13 survived the vitrification procedure whereas 59% of the blastocysts survived when they were cultured under paraffin oil both before vitrification and after warming. In experiment 2, another batch no. 7 of the same brand of silicone oil was compared with paraffin oil. No effect of the type of oil on embryonic development until the eight-cell stage could be demonstrated. However, the blastocyst formation rate was significantly lower with silicone oil batch 7 than with paraffin oil. The survival of vitrified blastocysts after warming was significantly improved when silicone batch 13 was replaced by batch 7 (0 and 41%, respectively) although it was still lower when compared with the survival of blastocysts developed under paraffin oil (53%) (p < 0.05). In further attempts to find the cause of the problem, the silicone and paraffin oils were analysed for Zn-contents (experiment 3). Zn-contents were comparable for silicone oil batch 13 (0.87 microM), silicone oil batch 7 (0.62 microM) and paraffin oil (0.73 microM). Media, conditioned by bovine oviduct epithelial cells cultured with a silicone or paraffin oil overlay were analysed by means of thin layer chromatography for differences in qualitative fatty acid composition. It was possible to detect that oil overlay changed the relative abundance of fatty acids in the different lipid classes. In the free fatty acid fraction, it was skewed in favour of palmitic acid and in cholesterol esters and phospholipids in favour of linoleic acid. It appears that due to the changed lipid contents of the medium, embryonic membranes are rendered more susceptible to freezing due to altered membrane composition or by membrane damage caused by lipid peroxidation.

Structural aspects of the zona pellucida of in vitro-produced bovine embryos: a scanning electron and confocal laser scanning microscopic study.

Structural aspects of the bovine zona pellucida (ZP) of in vitro-matured (IVM) oocytes and in vitro-produced (IVP) embryos were studied in two experiments to find a tentative explanation for the zona's barrier function against viral infection. In Experiment 1, the ultrastructure of the outer ZP surface was studied. The diameter (nm) and the number of the outer pores within an area of 5000 microm(2) of 10 IVM oocytes, 10 zygotes, 10 8-cell-stage embryos, and 10 morulae were evaluated by scanning electron microscopy. In oocytes and morulae, the ZP surface showed a rough and spongy appearance with numerous pores. In zygotes, the ZP surface was found to have a smooth, melted appearance with only a few pores. In 8-cell-stage embryos, both surface patterns were found. The mean number (per 5000 microm(2)) and the mean diameter of the outer pores were different between the four stages of development (P < 0.001): 1511 pores in oocytes, 1187 in zygotes, 1658 in 8-cell-stage embryos, and 3259 in morulae, with mean diameters of 182, 223, 203, and 155 nm, respectively. In Experiment 2, the continuity of the meshes (network of pores) towards the embryonic cells was examined by confocal laser scanning microscopy. Therefore, the passage through and the location in the ZP of fluorescent microspheres, with similar dimensions as bovine viral diarrhea virus (BVDV, 40-50 nm) and bovine herpesvirus-1 (BHV-1; 180-200 nm), were evaluated. For all stages, the smallest beads were detected halfway through the thickness of the ZP, whereas the beads with a size of 200 nm were found only within the outer-fourth part of the ZP. It can be concluded that the intact ZP of bovine IVM oocytes and IVP embryos are constructed in such a way that BVDV and BHV-1 should not be able to traverse the ZP and reach the embryonic cells. However, the risk exists that viral particles can be trapped in the outer layers of the ZP.

Cell allocation and chromosomal complement of parthenogenetic and IVF bovine embryos.

Considerable concerns exist regarding the quality of parthenogenetically activated embryos in terms of sufficient numbers of cells comprising the inner cell mass (ICM) and trophectoderm (TE) and the ploidy. Therefore, these two parameters were used to assess the quality of embryos derived from parthenogenetic activation by using calcium ionophore A23187 (CaI) followed by either 6-dimethylaminopurine (6-DMAP, 3.5 hr or 6.5 hr) or cycloheximide (CHX) plus cytochalasin D (CD). The conventional in vitro (IVF) produced embryos served as a control. Double staining of the parthenogenetic blastocysts showed that the total cell number (TC) of embryos from the 6-DMAP 3.5 hr (87.0 +/- 5.3) and CHX+CD (79.0 +/- 6.1) groups was not different (P > 0.05), but was lower than that of control embryos (116.0 +/- 5.8, P < 0.001). The mean ratios of inner cell mass (ICM) and trophectoderm (TE) cells in the 6-DMAP 3.5 hr group (0.57 +/- 0.04) and the control IVF group (0.50 +/- 0. 02) did not differ significantly. Both were higher than those of the CHX+CD group (0.36 +/- 0.02; P < 0.05). Further analysis of chromosomal compositions of developing stage embryos at day four after IVF or parthenogenetic activation demonstrated that prolonged treatment with 6-DMAP for 6.5 hr resulted in a significantly lower percentage of diploid embryos and a significantly higher percentage of abnormal ploidy embryos compared to treatment with 6-DMAP for 3.5 hr or with CHX and IVF. In conclusion, parthenogenetic activation of bovine oocytes with CaI followed by 6-DMAP for 3.5 hr could produce better quality embryos in terms of total cell numbers, the number of cells allocated to the ICM, and the ploidy of embryos.

Dental wear in horses in relation to the microhardness of enamel and dentine.

The microhardness of enamel, primary dentine and secondary dentine was determined in the incisor teeth of 39 horses of three different breeds, trotter horses, Belgian draft horses and Arab horses. Using a microhardness tester fitted with a Knoop diamond indenter, the overall Knoop Hardness Number was determined for each tissue, and the influence of breed and age on the hardness were evaluated. Enamel and secondary dentine were significantly harder in Arab horses than in trotters and Belgian draft horses, but there were no significant differences between draft horses and trotter horses in the hardness of their enamel and dentine.

Effects of long-term treatment with bovine somatotropin on follicular dynamics and subsequent oocyte and blastocyst yield in an OPU-IVF program.

Fourteen Holstein-Friesian heifers between 15 and 22 months of age with normal reproductive tracts were used in an experimental set up to investigate the effect of a long term rBST-treatment on the follicular population prior to transvaginal ovum pick-up (OPU). The estrous cycle of the animals was synchronized by means of a double injection of 2 ml cloprostenol 11 days apart. The heifers were divided in 2 equal groups (n = 7) in which the animals had the same average body weight, one group receiving a weekly subcutaneous injection of 640 mg recombinantly derived bovine somatotropin (rBST) on Mondays (rBST-treatment group) and a control group, being injected with 10 ml of saline. Heifers in both groups were submitted to OPU twice a week on Mondays and Thursdays using a 5 Mhz transducer and a disposable, 55 mm long, 20-g short bevelled needle at a vacuum pressure corresponding to approximately 13 ml water/min. The experimental period lasted for 10 weeks (April to June), each animal receiving a total of 10 injections and being submitted to OPU for 20 times. Oocytes were subsequently matured and cultured in a separate drop per cow following conventional IVF procedures. A blood sample was taken on heparin immediately after each OPU session, for determination of blood progesterone concentrations to assess the influence of treatment and OPU procedure on the cow's estrous cycle. Although results show a significant increase in the total number of follicles and medium sized follicles in the rBST-treated group, no statistically significant different number of retrieved oocytes between the rBST-treated and nontreated group could be detected. The average number of retrieved oocytes per session per cow was comparable, being 6.4 for the treated and 6.0 for the control group. Additionally, the average number of blastocysts per cow per session did not differ significantly between groups, being 1.41 in the rBST-treated group and 1.53 in the control group. The number of cultured oocytes which developed to the blastocyst stage was 22% in the rBST-treated group, which was not significantly different from 25% in the control group. Repeated OPU appeared to induce a certain degree of acyclicity in both treated and nontreated animals.

Relationship between timing of development, morula morphology, and cell allocation to inner cell mass and trophectoderm in in vitro-produced bovine embryos.

Noninvasive measurements of bovine embryo quality, such as timing of cleavage, morula morphology, blastocyst formation, and hatching ability, were linked with the number of inner cell mass (ICM) cells and trophectoderm (TE) cells of the resulting embryos. First, it was confirmed that fast-cleaving embryos proved to have significantly higher chances to reach advanced developmental stages vs. intermediate and slow cleavers (P = 0.01). They also showed significantly less fragmentation at the morula stage, implying the presence of more excellent morulae among fast-cleaving embryos (P < 0.05). Second, the quality of hatched blastocysts, resulting from morulae of different morphological grades, was examined by differential staining. The total cell and ICM cell numbers were significantly lower for hatched blastocysts developed from poor morulae compared to hatched blastocysts developed from excellent, good, or fair morulae. However, hatched blastocysts with < 10 ICM cells were seen in embryos belonging to all four morphological scores. Finally, it was found that timing of first cleavage was not significantly correlated with timing of blastocyst formation or with cell number of blastocysts. Timing of blastocyst formation, however, was significantly correlated with cell number: day 8 blastocysts had significantly lower total cell and ICM cell numbers than day 6 and day 7 blastocysts (P < 0.001). These results suggest that the quality of in vitro-produced bovine embryos is very variable and cannot be linked with a single criterion such as embryo morphology and/or hatching ability. Timing of blastocyst formation was the most valuable criterion with regard to embryonic differentiation.

Effects of needle tip bevel and aspiration procedure on the morphology and developmental capacity of bovine compact cumulus oocyte complexes.

Effects of the needle tip bevel and the aspiration procedure on the morphology of cumulusoocyte-complexes (COCs) and the developmental capacity of the oocytes after IVF were studied in 2 in vitro oocyte pick-up (OPU) simulations using a disposable ovum pick-up needle guidance system. In Experiment 1, the influence of the length of the needle bevel was investigated using a short and a long bevelled 20-g disposable needle. After being aspirated from slaughterhouse ovaries, the retrieved COCs were divided into 3 categories: 1) oocytes surrounded by a compact cumulus, 2) oocytes with an expanded cumulus, 3) partially naked oocytes. In Experiment 2, the influence of 5 different levels of aspiration vacuum for 3 different needle diameters (18-g, 19-g, 20-g) and 2 different needle bevels (long, short) was tested on the recovery and on the morphology of the cumulus investment of a fixed number of previously scored compact cumulus oocytes complexes (CCOCs), retrieved after slicing slaughterhouse ovaries. The re-retrieved COCs were allocated to Categories 1 and 3. The results show that the length of the needle bevel has a significant effect on oocyte recovery, in favor of the long-bevelled needle. As soon as higher aspiration vacua are used, a decrease of the number of CCOCs can be observed, which is less prominent for the short-bevelled needle compared to the long-bevelled one. The final number of blastocysts is similar for both needle types. In Experiment 2, the disposable needle system proved to be highly effective since nearly 80% of the CCOCs were retrieved. At low aspiration vacuum, up to 90% of the CCOCs withstand the aspiration procedure undamaged. Increasing the aspiration vacuum results in a decrease of the number of CCOCs, which is less pronounced using thinner needles. Averaged over all needle types, the prevalence of blastocysts expressed relative to the number of recovered oocytes decreases with higher aspiration vacuum.

Sucrose-induced shrinkage of in vitro produced bovine morulae: effect on viability, morphology and ease of evaluation.

Sucrose (0.3 M) was used to cause artificial compaction of the embryonic cell mass of in vitro produced bovine embryos to facilitate morphological evaluation. Embryos were produced using routine in vitro maturation (IVM) and fertilization (IVF) techniques. The time necessary to induce shrinkage in 0.3 M sucrose to 75% of the original volume of Day 5 morulae was found to be less than l min, and 95% of the volume was regained in PBS after 2.5 min. No detrimental effect was observed after a 5- to 10-min sucrose treatment on subsequent blastocyst formation at Days 6 and 7 (P > 0.05). Furthermore, no significant differences were observed in the total number of cells, or in the mitotic and pycnotic cell index of blastocysts in different treatment groups. Agreement among 7 evaluators grading 40 Day 6 embryos was examined using the kappa coefficient of agreement (kappa). Overall agreement among evaluators for classification of quality grade was poor (48.2 %, kappa = 0.31) for embryos evaluated in PBS, but the rate improved when the same embryos were scored in sucrose (62.5 %, kappa = 0.49). Evaluating less compact in vitro produced bovine morulae in sucrose increases agreement among evaluators, since embryos in sucrose mimick the appearance of in vivo produced embryos. Thus, we conclude that scoring in vitro produced embryos in sucrose improves agreement among evaluators.

Circulating antigen levels in serum of cattle naturally infected with Schistosoma mattheei.

Levels of 2 Schistosoma circulating antigens, the circulating anodic antigen (CAA) and the circulating cathodic antigen (CCA), were determined in serum samples collected, on a monthly basis over a period of 1.5 years, from 32 farm animals of different ages and from 12 tracer calves exposed to Schistosoma mattheei infection on a Zambian farm. Faecal egg counts were monitored in all animals and worm burdens in tracers determined after perfusion. Antigen determination tests in serum, with sensitivities between 95 and 100% in heifers and adult cows, proved to be excellent tools for the diagnosis of cattle schistosomiasis. Also in young calves, some infections could be demonstrated earlier by CCA determination than by faecal egg examination. A poor correlation was seen between the data for faecal egg counts and for CAA and CCA levels. It therefore appears that circulating antigen measurements in serum are of limited value as indicators of the pathogenesis of infection in cattle. Although all tracer calves were found infected at perfusion, large variations were recorded in antigen levels. An unexpected finding was the observation in farm animals of a clear seasonal pattern in CAA levels, with significant increase between August and October during the second half of the dry season, when animals are subjected to heavy physical and nutritional stress. It therefore appears that, although circulating antigen determination may provide an indication of the worm burden in ageing infections, possible variations of antigen clearance rate with the physiological condition of the host may complicate the interpretation of the results.

Cell allocation to the inner cell mass and the trophectoderm in bovine embryos cultured in two different media.

Data from other laboratories have shown that speed of bovine blastocyst development is higher when Ménézo B2 is used for coculture compared to TCM199. It was our purpose to investigate whether this early blastocyst formation was also indicative of embryo quality by studying the allocation of inner cells in embryos generated by B2-coculture and by TCM199-coculture. For this purpose, a differential staining technique was used. General embryo development was similar for TCM199- and B2-embryos expressed as rate of cleavage at day 3 and morula-blastocyst formation at day 8 (P > 0.05), but significantly different when expressed as number of eight-cell stages at day 3 and expanded or hatched blastocysts at day 8 (P < 0.01). B2-embryos cultured until day 5, 6, and 7 post insemination, had total cell numbers of 24, 65, and 109 respectively, which was significantly higher than the cell number of TCM199-embryos cultured over the same time period (18, 41, and 71 respectively, P < 0.001). Morphological differentiation was significantly more advanced for B2-embryos at day 7 and 8 (P < 0.0001 and P < 0.001, respectively). First presumptive inner cells appeared in eight- to 16-cell stages at day 3. Because the determination of inner cells by differential staining is depending upon the presence of functional tight junctions, we concluded that the establishment of the tight junction seal in B2-embryos differed from that in TCM199-embryos: Inner cells appeared 0.56 cell cycle later in B2-embryos (P < 0.001) and a larger variation existed in the number of ICM-cells in B2-blastocysts (P < 0.001). The higher total cell number of B2-expanded blastocysts was mainly acquired by trophectoderm growth (P < 0.06). These data indicate that the apparent better quality of B2-embryos (faster cleavage, earlier blastocyst formation) is not reflected in a reliable number of inner cells of B2-blastocysts.

Oxygenation activity of chicken blood phagocytes as measured by luminol- and lucigenin-dependent chemiluminescence.

Luminol- and lucigenin-dependent chemiluminescence (CL) was used to compare activation of the respiratory burst of chicken peripheral blood monocytes and heterophils after stimulation with various agents. Monocytes and heterophils were obtained from the blood of three specific-pathogen-free chickens at 14 months of age and purified by a two-step discontinuous Percoll gradient. All cells responded to phorbol 12-myristate 13-acetate (PMA), zymosan A and calcium ionophore A23187 producing CL. The time course of luminol- and lucigenin-dependent CL was similar for both monocytes and heterophils after stimulation with PMA or zymosan A. Heterophils at lower cell number than monocytes responded with similar or higher peak maximum (PM) values. At the concentrations of stimuli used, the order of mean PM values was: zymosan A > PMA > A23187. Addition of 4 x 10(-6) M N-formyl-1-L-methionyl-L-leucyl-L-phenylalanine (fMLP) showed weak but significant CL activity at 1 x 10(6) monocytes per tube with luminol and at 5 x 10(6) monocytes per tube with lucigenin. No significant response to fMLP was observed with heterophils. The results indicate that the respiratory burst of chicken monocytes and heterophils can be measured by CL.

Effects of aspiration vacuum and needle diameter on cumulus oocyte complex morphology and developmental capacity of bovine oocytes.

The effects of aspiration vacuum and needle diameter on the morphology of the cumulusoocyte-complex (COC) and developmental capacity of the oocyte after IVF was studied in 2 experiments using a disposable ovum pick-up needle guidance system whose construction permits its use in vitro. In Experiment 1, the relationship was determined between the aspiration vacuum, expressed in millimetre of mercury, and the actual amount of water aspirated by the system, expressed in millilitre per minute. In Experiment 2, five different levels of aspiration vacuum for 3 different needle diameters (18g, 19g and 21g) were tested in slaughterhouse ovaries. The cumulus-oocyte complexes (COCs) were divided into 3 categories: 1) oocytes with a compact cumulus, 2) oocytes with an expanded cumulus and 3) naked oocytes. The results show that a change of needle diameter can triple the amount of fluid actually aspirated. The highest oocyte recovery rates are obtained when using the thickest needle (18-g), regardless of the aspiration vacuum. On the average, for all needle types, more oocytes are recovered at the highest aspiration vacuum. For all needle diameters, the proportion of oocytes surrounded by a compact cumulus decreases progressively as the vacuum increases. Regardless of the vacuum applied, thinner needles result in a higher proportion of recovered COCs with a compact cumulus. At a high aspiration vacuum, naked oocytes become predominant regardless of the needle diameter. The prevalence of blastocysts, expressed in proportion to the recovered COCs, decreases as the aspiration vacuum increases, being especially noticeable between 70 and 130 mm Hg.

Observations on worm population dynamics in calves naturally infected with Schistosoma mattheei.

The evolution of faecal egg output, worm burdens and tissue egg counts in young calves was monitored during the first year of natural exposure to Schistosoma mattheei infection on a Zambian farm. According to the duration of their stay on the farm, these calves were classified into 2 groups of 14 temporary tracers (TT calves) which were introduced on a 2-monthly basis for residential periods of 2 months, and 12 permanent tracers (PT calves) introduced either at the beginning of the experiment (Group A) or 2 months later (Group B) and gradually removed after residential periods of 2, 4, 6, 8, 10 and 12 months on the farm. Worm counts in the TT calves showed that infection occurred throughout the year on the farm and that levels of infection acquired during each period of 8 weeks correlated well with the respective infected snail densities observed at the main transmission site. Marked differences in worm population dynamics were recorded between the 2 groups of PT calves. In Group B animals which apparently were initially exposed to heavy transmission, according to the results from TT calves, much higher worm counts and greater susceptibility to reinfection were observed than in Group A animals initially exposed to lighter exposure. These results suggest that the development of resistance to natural infection with S. mattheei may depend on the initial exposure to the parasite. Low initial exposures may lead to resistance whereas high initial exposures may result in decreased immune responses resulting in susceptibility to infection.

Optimization of a simple vitrification procedure for bovine embryos produced in vitro: effect of developmental stage, two-step addition of cryoprotectant and sucrose dilution on embryonic survival.

Experiments were designed to determine optimal conditions for the cryopreservation of bovine embryos produced in vitro. In Expt 1, embryos were exposed for 1, 3 or 5 min to a vitrification solution consisting of 40% (v/v) ethylene glycol, 18% (w/v) Ficoll and 10.26% (w/v) sucrose (EFS) and were subsequently vitrified. After warming in water at room temperature and diluting in a solution of 0.25 mol sucrose l-1, the in vitro survival rate in Ménézo-B2 medium was highest after exposure to EFS for 1 min. In Expt 2, embryos at day 7 and day 8 were vitrified after exposure to EFS for 1 min. The survival rate of embryos at day 7 was significantly improved, especially at the blastocyst and expanded blastocyst stage, when the Ménézo-B2 medium was supplemented with bovine oviduct epithelial cells (BOEC). Embryos at day 8 exhibited a significantly lower survival rate than did embryos at day 7 in both culture media. In Expt 3, one-step exposure of embryos to EFS for 1 min was compared with two-step exposure to 20% ethylene glycol for 3 min and EFS for 30-45 s. Embryos exhibited significantly higher survival and hatching rates after two-step vitrification, especially at the expanded blastocyst (89% and 69%, respectively) and the blastocyst stage (75% and 38%, respectively). In Expt 4, embryos were diluted in solutions of 0, 0.25 or 0.5 mol sucrose l-1 after two-step vitrification. There were no significant differences in the survival rates between the three dilution treatments.(ABSTRACT TRUNCATED AT 250 WORDS)