Effect of genetic merit, milk yield, body condition and lactation number on in vitro oocyte development in dairy cows

The effects of milk yield, body condition score (BCS) and lactation number on the number of oocytes recovered and blastocysts formed were studied following in vitro maturation, fertilization and culture of bovine oocytes collected from 48 high and 46 medium genetic merit dairy cows in their first and third lactation. The cows were slaughtered between 125 and 229 d post partum. Ovaries were recovered, and 2- to 10-mm follicles were aspirated. Cleavage rate and number of blastocysts were determined at 44 h and 7 d after insemination, respectively. Oocytes from high genetic merit cows formed fewer blastocysts and had lower cleavage and blastocyst formation rates than those from medium genetic merit cows (0.36 +/- 0.19, 70.4 and 6.8% vs 0.85 +/- 0.22, 77.4 and 11.4%, respectively). The effect of milk production was tested by grouping cows in their third lactation into high and low groups. There was no difference in number of oocytes recovered and subsequent development into blastocysts between the cows in the high milk production group (4559 to 5114 kg, n = 20) and cows in the low yield (3162 to 3972 kg, n = 20) group (6.9 +/- 1.34 vs 8.9 +/- 1.32, respectively). The effect of BCS was tested by grouping cows in their first or third lactation into high and low groups. Cleavage and blastocyst formation rates were greater for oocytes from cows with a high BCS (3.3 to 4.0, n = 20) than a low BCS (1.5 to 2.5, n = 20) (75.7 vs 61.9% and 9.9 vs 3.0%, respectively). Cows in the first lactation yielded fewer oocytes (5.7 +/- 1.24) than cows in the third lactation (7.8 +/- 0.79). Thus, the quality of oocytes probably contributes to reduced fertility, often evident in high genetic merit dairy cows.

Effects of superovulated heifer diet type and quantity on relative mRNA abundances and pyruvate metabolism in recovered embryos

This study investigated the effects of quantity and type of diet fed to superovulated donor heifers on molecular and metabolic indices of embryonic development. These effects included the relative abundances of mRNAs for the alpha 1 subunit of Na/K-ATPase and the antioxidant enzyme Cu/Zn-SOD, as well as pyruvate utilization in bovine morulae and blastocysts developed in vivo. Heifers were fed a daily ration of either grass silage and a citrus-beet pulp-based concentrate or grass silage and a barley-based concentrate for 116 days, both at 3 kg per day or ad libitum. In embryos derived from heifers fed the pulp-based diets, the relative abundances of the transcripts were not affected by either day of collection or quantity of diet. In embryos derived from heifers fed the barley-based diets, the relative abundances of the Na/K-ATPase transcripts were also not changed by these main effects, while the relative abundances of the Cu/Zn-SOD transcripts were affected by day of collection and by the quantity of diet. Pyruvate metabolism was affected by day of collection, and was significantly increased in day 8 embryos compared with day 7 and day 6 embryos. Diet quantity did not affect pyruvate utilization, whereas diet type did increase pyruvate metabolism in the barley group when compared with the pulp group. The results of this study show for the first time that molecular and metabolic variations may exist in embryos derived in vivo and developed in donor heifers on nutritional regimens differing in type and quantity. Differences in embryos collected on different developmental days may be attributed to varying cell numbers. Alterations in the relative abundances of the Cu/Zn-SOD transcripts and pyruvate metabolism caused by the quantity of diet fed to the donor animal were likely to have been due to alterations in metabolic end products that accumulate in reproductive tract fluids, whereas differences in embryonic metabolism caused by type of diet are related to the composition of the diet. These findings characterize embryos produced in vivo at the molecular level, indicating that the molecular markers used in the present study can differentiate between populations of embryos produced under different nutritional regimens and determine conditions conductive to the production of good quality embryos.

Effects of superovulated heifer diet type and quantity on relative mRNA abundances and pyruvate metabolism in recovered embryos

This study investigated the effects of quantity and type of diet fed to superovulated donor heifers on molecular and metabolic indices of embryonic development. These effects included the relative abundances of mRNAs for the alpha 1 subunit of Na/K-ATPase and the antioxidant enzyme Cu/Zn-SOD, as well as pyruvate utilization in bovine morulae and blastocysts developed in vivo. Heifers were fed a daily ration of either grass silage and a citrus-beet pulp-based concentrate or grass silage and a barley-based concentrate for 116 days, both at 3 kg per day or ad libitum. In embryos derived from heifers fed the pulp-based diets, the relative abundances of the transcripts were not affected by either day of collection or quantity of diet. In embryos derived from heifers fed the barley-based diets, the relative abundances of the Na/K-ATPase transcripts were also not changed by these main effects, while the relative abundances of the Cu/Zn-SOD transcripts were affected by day of collection and by the quantity of diet. Pyruvate metabolism was affected by day of collection, and was significantly increased in day 8 embryos compared with day 7 and day 6 embryos. Diet quantity did not affect pyruvate utilization, whereas diet type did increase pyruvate metabolism in the barley group when compared with the pulp group. The results of this study show for the first time that molecular and metabolic variations may exist in embryos derived in vivo and developed in donor heifers on nutritional regimens differing in type and quantity. Differences in embryos collected on different developmental days may be attributed to varying cell numbers. Alterations in the relative abundances of the Cu/Zn-SOD transcripts and pyruvate metabolism caused by the quantity of diet fed to the donor animal were likely to have been due to alterations in metabolic end products that accumulate in reproductive tract fluids, whereas differences in embryonic metabolism caused by type of diet are related to the composition of the diet. These findings characterize embryos produced in vivo at the molecular level, indicating that the molecular markers used in the present study can differentiate between populations of embryos produced under different nutritional regimens and determine conditions conductive to the production of good quality embryos.

A homologue of the Agrobacterium tumefaciens VirB and Bordetella pertussis Ptl type IV secretion systems is essential for intracellular survival of Brucella suis

Analysis of a TnblaM mutant of Brucella suis 1330, identified as being unable to multiply in Hela cells, allowed us to identify a 11 860 bp region of the B. suis genome encoding a type IV secretion system, homologous to the VirB system of Agrobacterium tumefaciens and the Ptl system of Bordetella pertussis. DNA sequence revealed 12 open reading frames (ORFs) encoding homologues of the 11 VirB proteins present in the pTi plasmid of Agrobacterium with a similar genetic organization, and a twelfth ORF encoding a putative lipoprotein, homologous to a protein involved in mating pair formation during bacterial conjugation and to adhesins used by Pseudomonas species to bind to plant roots. Phylogenetic trees based on the sequences of VirB4 and VirB9 protein homologues suggest that evolution of the systems from DNA transfer towards protein secretion did not stem from a single event but that the protein secretion systems have evolved independently. Four independent mutants in virB5, virB9 or virB10 were highly attenuated in an in vitro infection model with human macrophages. The virulence was restored by complementation with a plasmid containing the full virB region. The virB region appears to be essential for the intracellular survival and multiplication of B. suis.

Investigation into the role of the response regulator NtrC in the metabolism and virulence of Brucella suis

During infection, Brucella species have to adapt to a range of different environments. Environmental sensing in bacteria often involves the concerted action of two-component regulatory systems consisting of sensor and response regulator components. In this study, we identified, cloned and sequenced four independent response regulator gene fragments from Brucella melitensis. One amplified gene fragment showed nearly 90% identity to the response regulator subfamily of NtrC transcriptional activators, and further analysis revealed the presence of an adjacent gene encoding the sensor protein NtrB. The NtrBC two-component regulatory system has been shown to play varying roles in nitrogen metabolism and potentially in virulence in other bacterial species. A B. suis ntrC isogenic mutant was constructed which showed no significant differences in growth rates compared to the wild-type strain when grown at different temperatures in vitro. However, the mutant exhibited a reduction in metabolic activity in the presence of many amino acids. The mutation did not affect survival or multiplication of B. suis in macrophages, but during the initial stages of infection in the murine brucellosis model, the ntrC mutant showed a reduced ability to multiply rapidly in splenic tissue.

Effect of type and quantity of concentrates on superovulation and embryo yield in beef heifers

Embryo yield and quality can be decreased following superovulation of cattle on high levels of concentrates. Concentrate type can alter rumen fermentation patterns and so affect energy availability and thus embryo quality. The objectives of this experiment were to examine the effect of 2 levels and 2 types of concentrate on superovulatory response and embryo quality in beef heifers. Beef heifers received grass silage as a basal diet and barley at 3 kg (n = 20) or ad-libitum (n = 19), or citrus/beet pulp at 3 kg (n = 18) or ad-libitum (n = 19) as the source of concentrate supplement. Silage was available ad-libitum for heifers offered 3 kg but was restricted to 1 kg DM/day for heifers on ad-libitum concentrate intake. Both concentrates contained 14% crude protein. After 100 d, heifers were treated with an intravaginal progesterone releasing device (CIDR) for 7 d, and superovulation was initiated 60 h before CIDR withdrawal. Heifers received pFSH (a total of 265 mg NIH-FSH-P1 equivalent) administered over 8 injections at 12 h intervals with the last 2 injections administered at 12 and 24 h after CIDR withdrawal; they were inseminated at 56 and 72 h after CIDR withdrawal without reference to estrus. Heifers were slaughtered 6, 7 or 8 d after the first insemination, and embryos were flushed from the uterus with PBS and were graded morphologically. Statistical analyses were performed using analysis of variance. There was no interaction between level and type of diet, and thus data for the main effects are presented separately. Final live weights at the end of the experiment and carcass weights for heifers offered ad-libitum concentrate (643.8+/-6.9 kg; 354+/-8 kg, respectively) were higher (P<0.01) than those of heifers offered 3 kg concentrate (613.1+/-7.5 kg; 338.4+/-3.2 kg, respectively) while live weights and carcass weights of heifers offered barley (625.6+/-8.1 and 345.4+/-4.1 kg, respectively) or citrus/beet pulp concentrate (631.4+/-7.0 and 348.0+/-3.1 kg, respectively) were not different (P>0.05). Superovulatory responses (number of corpora lutea at slaughter) was greater (P<0.06) when heifers were offered 3 kg (15.5+/-1.6) than when offered ad-libitum concentrates (12.3+/-1.4). However, the superovulatory response for both citrus/beet pulp (14.4+/-1.5) and barley (13.4+/-1.5) diets were not different (P>0.05). Heifers offered 3 kg concentrates produced greater (P<0.05) numbers of transferable embryos (4.8+/-0.7) compared with heifers fed ad-libitum concentrates (2.8+/-0.4). Heifers offered citrus/beet pulp produced greater (P<0.05) numbers of transferable embryos (4.8+/-0.7) than heifers offered barley (2.9+/-0.5). These data indicate that high concentrate intake has a negative effect on embryo yield and quality and that a barley compared with citrus/beet pulp based concentrate has a negative effect on embryo quality following superovulation in beef heifers.

Effect of immunization against melatonin on prolactin concentrations and the timing of reproductive transitions in ewes

The objective of this experiment was to develop a procedure for immunizing ewes against melatonin that would alter the effects of changing photoperiod on seasonal reproduction and prolactin secretion. Ewes were immunized against human serum albumin (HSA) as controls (n = 9) or a melatonin-human serum albumin conjugate (0.25 mg; n = 10) on December 14th (Day 0) and boosted 9 times. They were maintained on natural photoperiod and then transferred indoors and exposed to long days for 35 d, followed by short days for 146 d, long days for 93 d, and short days for a further 123 d. Antibody titers to melatonin (at a serum dilution of 1:1,250) were significantly higher in immunized ewes (27.3 +/- 6.6%) than controls (0.7 +/- 0.1%; P < 0.001). At the end of the experiment, antibody titers in immunized ewes (at dilution of 1:50) were higher in blood (43.7 +/- 8.2%) than in cerebrospinal fluid (10.8 +/- 3.9%; P < 0.05), and highly correlated (r2 = 0.746). Onset of the breeding season was advanced slightly after the second transfer from long to short days in immunized ewes (April 12 +/- 3 d) compared with controls (April 25 +/- 3 d; P < 0.05). Mean serum prolactin concentrations were lower (P < 0.05) in melatonin-immunized ewes compared with controls on natural photoperiod, after transfer from long to short days, during long days, and after the second transfer from long to short days. In conclusion, despite melatonin-immunization increasing antibody titers in blood and cerebrospinal fluid, and decreasing prolactin concentrations over much of the experiment, minimal effects on the timing of reproductive transitions in the ewes were evident. This discrepancy between the response of the prolactin and reproductive axes to melatonin immunization supports the hypothesis of a dual site of action of melatonin, with melatonin acting in the pituitary gland to mediate the effects of photoperiod on prolactin secretion and in the mediobasal hypothalamus to affect reproductive responses.

Effect of roughage type and concentrate supplementation on follicle numbers and in vitro fertilisation and development of oocytes recovered from beef heifers

Increasing dietary energy tends to decrease the ovulatory response and produce fewer viable embryos following superovulation of beef cattle. Data in sheep indicate that high energy intake can decrease progesterone concentrations (P4), although effects in cattle are not as clear. The objectives were to evaluate the effects of roughage type and concentrate supplementation on P4 concentrations, follicle growth and subsequent oocyte fertilisation and embryo development in vitro. Forty-two beef heifers were allocated to 3 treatment groups: (i) silage ad libitum plus 6 kg concentrates (silage + conc.; n = 14); (ii) silage ad libitum (silage; n = 14) or (iii) hay ad libitum (hay; n = 14) for 40 days. Oestrus was synchronised using a controlled intravaginal progesterone releasing device (CIDR) for 7 days plus prostaglandin F2 alpha (15 mg luprostiol) administered 2 days before CIDR withdrawal. Ovaries were stimulated with 600 i.u. of follicle stimulating hormone (pFSH) administered in 6 equal doses at 12-h intervals, starting 12 days after CIDR withdrawal. Daily blood samples were collected from 3 days after CIDR insertion until CIDR withdrawal, and for another 3 days prior to pFSH, for P4 determination. Oocytes were recovered postmortem 12 h after the last pFSH injection, matured, fertilised and cultured in vitro. There was no overall effect of diet (P > 0.05) on P4 concentrations. The number of follicles grown in heifers on silage + conc (18.8 +/- 3.3), silage (23.5 +/- 3.4) or hay (18.1 +/- 2.6) were not affected by the dietary treatment (P > 0.05). The percentage of oocytes fertilised from heifers on hay (88%) was higher compared to oocytes from heifers on silage (79%; P < 0.05), but was not different (P > 0.05) compared to the proportion of oocytes from heifers on silage + conc. (86%). The percentage of fertilised oocytes that cleaved was higher from heifers on silage (94%; P < 0.01) compared with oocytes from heifers on hay (82%) or silage + conc. (86%). The proportion of embryos that developed to blastocyst was not different (P > 0.05) between groups of oocytes from heifers on silage + conc. (8%), silage (14%) or hay (15%). Heifers on silage produced numerically more blastocysts (silage: 19 from 14 heifers; silage + conc.: 8 from 14 heifers; hay: 12 from 14 heifers). These results suggest that dietary treatment used prior to oocyte recovery did not significantly influence the developmental competence of the oocytes in vitro.

Seasonal variation in long-day stimulation of prolactin secretion in ewes

Whereas ewes initiate reproductive activity in response to a photoperiod signal initiated after the winter solstice of 35 long days (35 LD) followed by short days, the reproductive axis fails to respond to this signal between the autumn equinox and the winter solstice. The aim of experiment 1 was to determine whether the prolactin axis, like the reproductive axis, is unresponsive to a 35 LD photoperiod signal followed by continuous exposure to short days between the autumn equinox and the winter solstice. Whereas the 35 LD signal from September 21 (</= 6 h increase in day length) failed to influence prolactin secretion, all other long-day treatments (> 6 h increase in day length) initiated a rise in prolactin in at least 75% of ewes in each group (p < 0.05). The aim of experiment 2 was to determine whether ewes failed to secrete prolactin during a 35 LD photoperiod from September 21 because they did not recognize a 6-h increase in day length at any time of year as a stimulatory photoperiod signal or because hypothalamic/pituitary regulation of prolactin synthesis or secretion is compromised in September. The results demonstrated that while hypothalamic regulation of prolactin secretion and pituitary stores of prolactin were normal at all times of year examined, the ability of ewes to secrete prolactin in response to a long-day photoperiod signal appears to be dependent on photoperiodic history rather than the time of year of the photoperiodic challenge.

The influence of short-term nutrient changes on follicle growth and embryo production following superovulation in beef heifers

Acute decreases in nutrient intake can improve embryo quality in sheep, although reductions in ovulation rate can also occur. In cattle, short-term nutrient restriction prior to ovulation has been shown to increase subsequent pregnancy rates. Thus, the objective was to determine the effect of a severe reduction in food intake on follicle growth and embryo quantity and quality in heifers superovulated with FSH. Beef heifers (n = 61) were offered a diet of grass silage and concentrates (ratio of 5:1, on a fresh weight basis), which was adjusted to provide a predicted intake of 28.6 Mcal/kg ME/d (H) or 9.6 Mcal/kg ME/d (L). Heifers were synchronized with a progesterone-releasing device for 7 d. They were allocated to oocyte recovery (n = 16/treatment) after 3 (225 IU) or 8 (600 IU) injections of FSH given at 12-h intervals. Oocytes were matured, fertilized and cultured individually in vitro. The remaining heifers (n = 14/treatment) were superovulated using FSH (600 IU), and embryos were recovered 7 d after breeding. The embryos were morphologically graded and subsequently cultured for 24 h before differential staining to determine inner cell mass and trophectoderm cell numbers. Follicle numbers increased following 8 (16.6 +/- 2.0) compared with 3 (6.7 +/- 0.6) injections of FSH (P < 0.0001). Heifers on the L diet had more follicles than those on the H diet (13.5 +/- 2.4 vs 9.6 +/- 1.2; P < 0.06), which was predominantly due to an increase in the number of 7- to 10-mm follicles. However, this effect was only evident after 8 injections of FSH. There was no nutritional effect on cleavage rates in vitro (55.6 +/- 8.1 vs 53.8 +/- 9.0 for H vs L diets, respectively). However, cleavage rates were lower in oocytes collected after 8 than after 3 injections of FSH (31.3 vs 69.2%; P < 0.0001). There was no significant effect of nutrition on ovulation rate after FSH (14.4 +/- 1.9 vs 16.3 +/- 3.0 for H vs L diet, respectively). The number of embryos recovered was not different between heifers on H (10.4 +/- 1.3) and L (11.3 +/- 2.4) diets. Following culture for 24 h, a significantly higher proportion of embryos from heifers on the L diet developed to the blastocyst stage (72.9 vs 41.5%; P < 0.01). Total cell numbers on Day 8 were greater in embryos from heifers on the L diet (98.3 vs 75.4; P < 0.0001); yet the inner cell mass as a percentage of total cells was not different (21 vs 20%). These data indicate that low energy intake prior to and during superovulation resulted in more follicles and in improved embryo quality, as evident from the increased number of blastocysts formed and higher cell numbers.

Effect of timing of oestradiol benzoate injection relative to gonadotropin treatment on superovulatory response, and on embryo yield and quality in beef heifers

Variation in superovulatory responses in cattle may be related to the stage of follicular growth at the time of gonadotropin treatment. Waves of follicle growth are regulated by both follicle-stimulating hormone (FSH) and oestradiol. The objective of experiment 1 was to determine the dynamics of follicle wave emergence and the relationship with FSH and oestradiol concentrations, after treatment of heifers with oestradiol benzoate (ODB) in the presence of an intravaginal progesterone-releasing device (CIDR-B). Experiment 2 examined the superovulatory response, embryo yield and quality following treatment with porcine follicle-stimulating hormone (pFSH) at different times relative to ODB injection. In experiment 1, 28 beef heifers were treated with a CIDR for 9 days and allocated at random to one of four groups to receive either: (I) CIDR only, or 5 mg ODB given as a single intramuscular injection at (II) day 0 (d0); (III) day 1.5 (d1.5); or (IV) day 3 (d3) post CIDR insertion. Ovaries were examined using daily ultrasound and blood samples were collected twice daily for 11 days. In experiment 2, 96 heifers were treated with a CIDR and 5 mg ODB as in experiment 1, and were allocated using a 4 x 3 factorial design plan to a superovulation programme using three doses (400 IU; 600 IU; 800 IU) of pFSH. FSH was given for 4 days at 12-h intervals beginning 6.5 days after CIDR insertion. Heifers received prostaglandin analogue 12 h before CIDR removal and were inseminated (AI) at 48 and 60 h post CIDR withdrawal and embryos were recovered 7 days after AI. In experiment 1, the interval from CIDR insertion to follicle wave emergence (FWE) was longer (P < 0.05) in heifers treated with ODB at d1.5 (5.4 +/- 0.4 days) and d3 (5.1 +/- 0.6 days) compared to heifers treated with CIDR only (2.4 +/- 0.4 days). On the basis of time to proposed injection of pFSH heifers would have had follicle emergence 4.4, 2.3, 1.5 and 1.4 days prior to pFSH for groups I, II, III and IV, respectively. In experiment 2, heifers treated with ODB at d1.5 had a higher (P < 0.05) superovulatory response (18.2 +/- 1.7) than heifers treated at d3 (12.8 +/- 1.7), but superovulatory response in both groups did not differ (P > 0.05) from heifers treated at d0 (14.4 +/- 2.0) or with CIDR only (15.0 +/- 1.8). There were fewer (P < 0.05) freezable-grade embryos recovered from heifers treated with ODB at d0 (1.5 +/- 0.7) and d3 (2.1 +/- 0.5) compared to heifers treated at d1.5 (3.0 +/- 0.6) or in heifers treated with CIDR only (3.4 +/- 0.7). Increasing the dose of pFSH caused a linear increase in the superovulatory response (11.7 +/- 1.0, 15.8 +/- 1.4 and 18.0 +/- 1.9) and in the number of embryos recovered (5.8 +/- 0.9, 7.0 +/- 0.8 and 9.1 +/- 1.0) for 400 IU, 600 IU and 800 IU, respectively. In conclusion, heifers treated with ODB had wide variation in time to follicle wave emergence and there was not a consistent beneficial effect of pretreatment with ODB on embryo yield and quality following superovulation.

Identification, cloning and initial characterisation of FeuPQ in Brucella suis: a new sub-family of two-component regulatory systems

To cause disease, Brucella species have to adapt to a range of different environments. Environmental sensing and adaptive responses in bacteria often involve the concerted action of a two-component regulatory system, consisting of sensor and response regulator components. Amplification and sequence analysis of response regulators from Brucella species identified a response regulator sequence with 96% similarity to Rhizobium leguminosarum FeuP. In R. leguminosarum, the FeuPQ two-component system is involved in the regulation of iron uptake. A Brucella suis feuP isogenic mutant was constructed but was not attenuated in the murine brucellosis model. The survival and multiplication of the mutant in macrophages was also unaffected. The FeuPQ regulon represents a newly characterised sub-family of response regulators.

Differences in chromosome number and genome rearrangements in the genus Brucella

We have studied the genomic structure and constructed the SpeI, PacI and I-CeuI restriction maps of the four biovars of the pathogenic bacterium Brucella suis. B. suis biovar 1 has two chromosomes of 2.1 Mb and 1.15 Mb, similar to those of the other Brucella species: B. melitensis, B. abortus, B. ovis and B. neotomae. Two chromosomes were also observed in the genome of B. suis biovars 2 and 4, but with sizes of 1.85 Mb and 1.35 Mb, whereas only one chromosome with a size of 3.1 Mb was found in B. suis biovar 3. We show that the differences in chromosome size and number can be explained by rearrangements at chromosomal regions containing the three rrn genes. The location and orientation of these genes confirmed that these rearrangements are due to homologous recombination at the rrn loci. This observation allows us to propose a scheme for the evolution of the genus Brucella in which the two chromosome-containing strains can emerge from an hypothetical ancestor with a single chromosome, which is probably similar to that of B. suis biovar 3. As the genus Brucella is certainly monospecific, this is the first time that differences in chromosome number have been observed in strains of the same bacterial species.

Genome structure and phylogeny in the genus Brucella

PacI and SpeI restriction maps were obtained for the two chromosomes of each of the six species of the genus Brucella: B. melitensis, B. abortus, B. suis, B. canis, B. ovis, and B. neotomae. Three complementary techniques were used: hybridization with the two replicons as probes, cross-hybridization of restriction fragments, and a new mapping method. For each type strain, a unique I-SceI site was introduced in each of the two replicons, and the location of SpeI sites was determined by linearization at the unique site, partial digestion, and end labeling of the fragments. The restriction and genetic maps of the six species were highly conserved. However, numerous small insertions or deletions, ranging from 1 to 34 kb, were observed by comparison with the map of the reference strain of the genus, B. melitensis 16M. A 21-kb Spel fragment specific to B. ovis was found in the small chromosome of this species. A 640-kb inversion was demonstrated in the B. abortus small chromosome. All of these data allowed the construction of a phylogenetic tree, which reflects the traditional phenetic classification of the genus.

Structural and antigenic identification of the ORF12 protein (alpha TIF) of equine herpesvirus 1

The equine herpesvirus 1 (EHV-1) homolog of the herpes simplex virus type 1 (HSV-1) tegument phosphoprotein, alpha TIF (Vmw65; VP16), was identified previously as the product of open reading frame 12 (ORF12) and shown to transactivate immediate early (IE) gene promoters. However, a specific virion protein corresponding to the ORF12 product has not been identified definitively. In the present study the ORF12 protein, designated ETIF, was identified as a 60-kDa virion component on the basis of protein fingerprint analyses in which the limited proteolysis profiles of the major 60-kDa in vitro transcription/ translation product of an ORF12 expression vector (pT7-12) were compared to those of purified virion proteins of similar size. ETIF was localized to the viral tegument in Western blot assays of EHV-1 virions and subvirion fractions using polyclonal antiserum and monoclonal antibodies generated against a glutathione-S-transferase-ETIF fusion protein. Northern and Western blot analyses of EHV-1-infected cell lysates prepared under various metabolic blocks indicated that ORF12 is expressed as a late gene, and cross reaction of polyclonal anti-GST-ETIF with a 63.5-kDa HSV-1 protein species suggested that ETIF and HSV-1 alpha TIF are antigenically related. Last, DNA band shift assays used to assess ETIF-specific complex formation indicated that ETIF participates in an infected cell protein complex with the EHV-1 IE promoter TAATGARAT motif.

Influence of previous photoperiodic exposure on the reproductive response to a specific photoperiod signal in ewes

Two experiments were carried out to determine whether the reproductive response of ewes to a specific photoperiodic signal depends on the time of year that the signal is given, and, if so, whether this dependence can be attributed to the photoperiodic history of the ewes. The aim of experiment 1 was to expand upon previous findings that the reproductive response to a specific photoperiodic challenge in ewes previously maintained on natural photoperiod varies with time of year. Ewes were transferred at one of three times of year from natural photoperiod to photochambers and were immediately exposed to 35 long days (18L:6D) followed by continuous exposure to short days (8.5L: 15.5D); this treatment is referred to as LD-->SD. The three times of year when long days started corresponded to the beginning of the breeding season, the mid-breeding season, and early anestrus (September 21, December 21, March 21, respectively). In ewes exposed to LD-->SD beginning in September, the breeding season and subsequent anestrous season was not altered. In ewes exposed to LD-->SD beginning in December, the transition to anestrus was advanced (p < 0.05) relative to that in controls maintained in simulated natural photoperiod. Subsequently, half of these ewes resumed reproductive activity within 180 days; this occurred 131 +/- 8 days after transfer to short days. In contrast, all ewes exposed to LD-->SD beginning in March resumed reproductive activity; this began 100 +/- 3 days after transfer to short days (p < 0.05 versus December group). The purpose of experiment 2 was to assess the extent to which the difference in response to a photoperiodic challenge can be attributed to photoperiodic history. Ewes were maintained on short days from the winter solstice interrupted with 35 long days from March 21, June 21, September 21, or December 21. The majority of ewes exhibited an onset of reproductive activity after exposure to LD-->SD at the different times of year, and there was no group difference in latency to onset of reproductive activity. The duration of reproductive activity, however, was longer (p < 0.05) in ewes exposed to LD-->SD beginning in June than in the other groups. Thus we conclude that the seasonal difference in the ability of the photoperiodic challenge of long followed by short days to induce reproductive activity in ewes previously maintained outdoors can be attributed, in large measure, to photoperiodic history. Other factors, such as phase of the endogenous rhythm, however, may influence the duration of reproductive activity resulting from this photoperiodic challenge.

Effect of immunization of rams against bovine inhibin alpha 1-26 on semen characteristics, scrotal size, FSH, LH and testosterone concentrations

The effects of inhibin immunization on inhibin antibody titres, semen characteristics, scrotal size, fertility, FSH, LH and testosterone concentrations were determined by immunizing adult rams against bovine inhibin alpha 1-26-Gly-Tyr conjugated to human serum albumin (n = 16) in non-ulcerative Freund's adjuvant and DEAE:dextran (1:1) or adjuvant alone (n = 16) on days 0 (29 June), 30, 60, 191, 303 and 394. Blood samples were collected and bovine inhibin alpha 1-26-Gly-Tyr antibody titres and serum testosterone concentrations were determined. Each month, between days 174 and 417, semen was collected every 30 min to a maximum of 15 ejaculates over 7 h and scrotal circumference was measured. Ram fertility was recorded during natural service. FSH, LH and testosterone concentrations and GnRH-induced FSH and LH release were measured in a subgroup of immunized (n = 5) and control (n = 5) rams at frequent intervals. Antibody titres were variable among immunized rams (0-46% 125I-labelled bovine inhibin alpha 1-26-Gly-Tyr at 1:1600 serum dilution) but mean titres were consistently higher than in control rams (P < or = 0.001). Immunization did not alter the semen volume, output or quality of spermatozoa or ram fertility, but increased the mean scrotal circumference (37.6 +/- 0.8 cm versus 34.4 +/- 0.7 cm, P < 0.001). Mean FSH concentrations were higher in immunized rams during two intensive blood sampling periods (in June and August) (5.8 +/- 0.7 ng ml-1 versus 3.0 +/- 0.3 ng ml-1, P < 0.001 in June; and 4.8 +/- 0.9 ng ml-1 versus 2.0 +/- 0.3 ng ml-1, P < 0.02 in August), and were correlated with antibody titres (r2 = 0.3, P < 0.05 in June; and r2 = 0.8, P < 0.001 in August). Discrete FSH pulses were not detected. Immunization did not alter mean or basal testosterone or LH concentrations, or LH pulse frequency; LH pulse amplitude was increased (1.6 +/- 0.2 ng ml-1 versus 0.8 +/- 0.2 ng ml-1, P < 0.02) and was correlated with antibody titres (r2 = 0.6, P < 0.01). Immunization enhanced GnRH-induced FSH (P < 0.05) but not LH release. In conclusion, immunization of adult rams against bovine inhibin alpha 1-26 Gly-Tyr increased scrotal circumference, mean FSH concentrations and LH pulse amplitude, without altering semen characteristics, fertility, mean LH concentrations, LH pulse frequency or mean testosterone concentrations.

Investigation of the Actinobacillus actinomycetemcomitans genome by pulsed field gel electrophoresis

Pulsed field gel electrophoresis was used to investigate nineteen strains of Actinobacillus actinomycetemcomitans. The genome was found to contain a single chromosome whose size we estimate to be 2300 kb from the sum of restriction fragments generated with rare cutting endonucleases. We detected the presence of large plasmids with sizes ranging from 35 to 300 kb. In some strains, extrachromosomal elements constitute over 20% of the total genome. Comparison of the profiles of ApaI digests of the 19 strains showed a high degree of polymorphism with 13 different profiles, providing a new tool for epidemiological studies.

Response of Brucella suis 1330 and B. canis RM6/66 to growth at acid pH and induction of an adaptive acid tolerance response

Acid pH is an environmental stress often encountered by Brucella during both the "environmental" and the "pathogenic" stages of its life. We have investigated the behaviour of B. suis biovar 1 and B. canis in acid conditions. Growth at suboptimal pH was characterized by a dramatic reduction in growth yield due to an early onset of stationary phase. B. suis was more resistant to low pH than B. canis, which lysed at pH 4.6. Viable counts measured after a 4-h acid shock at pH 3.2 showed that the relative survival of B. suis was 1,000-fold greater than that of B. canis. An adaptive acid tolerance response (ATR) was induced in both species by culture at pH 5.8; however, while the acid-sensitive B. canis had more than a 2,000-fold increase in survival following acid shock at pH 3.2, the increase in survival of B. suis was only around 50-fold. The kinetics of the induction of ATR were followed: for B. suis, 1-2 h (1 generation) at pH 5.8 were required to induce acid tolerance (50-fold protection), and these levels remained constant over 24 h. B. canis became relatively acid-resistant after only 30-min exposure to pH 5.8. Levels of acid tolerance continued to increase and were maximal at 24 h. Stationary phase pH 7.2 cultures of either species did not exhibit acid resistance, suggesting that, like Salmonella, Brucella does not have an rpoS-controlled stationary phase acid resistance.