A functional eukaryotic promoter is contained within the first intron of the hGH-N coding region

Human growth hormone is frequently used as a reporter gene in studies addressing the regulation of eukaryotic promoters. Here we present evidence that the first intron of the hGH-N coding region contains a novel eukaryotic promoter which is able to direct the expression of hGH-N and luciferase reporter genes. The corresponding transcriptional initiation site is located downstream of the splice acceptor site of exon 2. This internal hGH-N promoter can interfere with the transcriptional control elements of a promoter linked to the hGH-N coding region and thereby complicate the interpretation of data obtained with hGH-N as a reporter gene.

A detailed analysis of pronucleus development in bovine zygotes in vitro: cell-cycle chronology and ultrastructure

The aim of the present experiment was to analyze the chronology of pronucleus development and DNA synthesis, as well as the ultrastructure of intranuclear bodies, in bovine zygotes produced in vitro. Bovine oocytes were matured and fertilized in vitro, and sperm penetration and pronucleus development were examined. DNA synthesis was investigated by sequential incubation with [3H]- and [14C]thymidine followed by autoradiography on semithin sections. Ultrathin sections for transmission electron microscopy were prepared from the same zygotes. Sperm penetration was noted for the first time at 4 hr after in vitro insemination and reached a maximum at 6 hr. Pronucleus formation was initiated at 4 hr, and up to at least 11 hr the maternal pronucleus was more developed than its paternal counterpart. DNA synthesis was initiated at 14-15 hr, and the S-phase lasted for 8-10 hr. The most prominent ultrastructural entities of the pronuclei were the nucleolus precursor bodies (NPBs). During the S- and G2-phases, the NPBs spatially associated with clusters of interchromatin-like granules. The two components were firmly attached to each other by an electron-dense reticulum. During the late G2-phase, the NPBs were apparently detached from the interchromatin-like granules and the electron-dense reticulum again. The interaction between the intranuclear bodies and granules appears to be comparable with the situation previously described for in vivo-produced bovine zygotes (J Laurincík et al., Mol Reprod Dev 43:62-69, 1996), except for the lack of vacuolization of the NPBs during the S-phase in vitro.

Genetic variation in functionally important domains of the bovine mtDNA control region

DNA sequences of the mitochondrial control region (CR) of 32 unrelated Austrian cattle were analysed in order to determine the extent of variability in functionally important domains. Using sequencing of PCR products, allele-specific PCR (AS-PCR) and primer introduced restriction analysis (PIRA), 43 differences were observed. They included 33 transitions, five transversions, one deletion and four differences in the number of consecutive cytosines. Twenty-three of these polymorphisms have not been reported before. In addition, we analysed all available European cattle sequences for this region. The transcriptional start sites, the conserved sequence block CSB 1 and both binding sites for the mitochondrial transcription factor mtTFA were highly conserved. We found a transition in each of the inter-specifically conserved Mt4 and Mt5 elements, three nucleotide substitutions in the termination-associated sequence TAS-A and six polymorphisms in the conserved sequence block CSB 2+3, a region which has been implicated in mitochondrial RNA processing.

Non-balanced mix of mitochondrial DNA in cloned cattle produced by cytoplast-blastomere fusion

We have investigated the transmission of parental mitochondrial DNA (mtDNA) in three clones of born cattle obtained by intraspecific cytoplast-blastomere fusion. Using allele-specific TaqMan PCR a low level transmission of blastomere mtDNA (DB mtDNA) into the cloned offspring was detected, thereby generating a heteroplasmic population of mtDNA. The amount of DB mtDNA was 13% and 18% in two animals of a clone which derived from a 24-cell morula and 0.6% and 0.4% in two calves of clonal origin derived from a 92-cell morula. These values are in accordance with the tendency expected for neutral mtDNA segregation that the fewer cell divisions that have occurred in the donor embryo, the higher the amount of DB mtDNA. We also found a strong decrease of DB mtDNA which was about three orders of magnitude in the third clone derived from a 52-cell morula stage.

Composition of parental mitochondrial DNA in cloned bovine embryos

We have investigated parental mitochondrial DNA (mtDNA) in cloned bovine embryos obtained by intraspecific cytoplast-blastomere fusion. Analysis of two-cell to blastocyst stage embryos revealed that in contrast to the exclusion of paternal (sperm) mtDNA during sexual inheritance in the cytoplast-blastomere fusion complexes, there was mixing and co-existence of parental mtDNA. The mixing of mtDNA was non-balanced with the minority deriving from the blastomere. The constant content of mtDNA during embryogenesis until the blastocyst stage suggesting an absence of mtDNA replication was shown for conventional 'in vitro fertilised' (IVF) embryos and for cloned embryos. The ratio of parental mtDNA was in accordance with the estimated quantitative participation of mtDNA from the fusion partners.

Transgenic approaches to the increase of disease resistance in farm animals

Molecular genetics and reproductive biology techniques enable the transfer of foreign DNA into mammals. Novel approaches to modify disease resistance or susceptibility in livestock are justified by economic and animal welfare concerns. Current research on the improvement of disease resistance by gene transfer focuses on three main strategies, as follows: a) somatic gene transfer, i.e., nucleic acid vaccines b) deletive germ-line gene transfer, i.e., gene knockout c) additive germ-line gene transfer. These strategies aim at either the transient or stable expression of components known to influence non-specific or specific host defence mechanisms, or the disruption of genes known to cause susceptibility to disease. Referring to the source of the effective agent and the site and mode of action, the strategies are termed 'genetic', 'congenital', 'intracellular' and 'extracellular' immunisation. Each gene transfer experiment has to be evaluated carefully with respect to the potential to create novel cases of pathogen resistance or to lose species barriers or cell-type restrictions.

OMEC II: a new ovine mammary epithelial cell line

We have established three independent ovine mammary epithelial cell lines which arose from primary cultures of ovine mammary epithelial cells by spontaneous immortalization. One of them, OMEC II, was characterised in greater detail. The cells grow on plastic dishes in medium containing 10% FCS without any requirement for additional growth factors or hormones. Immunofluorescence staining of this cell line showed expression of cytokeratin (46 kDa) and ZO-1, a tight-junction associated protein, but negative immunostaining for an anti-vimentin antibody. In confluent cell monolayers 'domes' because visible indicating the development of a polarised phenotype and the ability of directed secretion. When grown in collagen gels typical ducts with end-buds were observed. Treatment with lactogenic hormones increased the frequency of dome formation, but no expression of beta-lactoglobulin was found. To our knowledge this is the first report on an ovine mammary epithelial cell line.

A reliable procedure for differential staining of in vitro produced bovine blastocysts: comparison of tissue culture medium 199 and Ménézo's B2 medium

A reliable double-dye technique has been established for counting the number of inner cell mass and trophectoderm cells of in vitro produced bovine blastocysts. The latter were first incubated in a 1:2 dilution of a rabbit antiserum raised against a mixture of recombinant bovine interferon tau and serum containing medium conditioned by in vitro produced trophoblastic vesicles for 45 min at 39 degrees C. Subsequently, the blastocysts were incubated in a 5% (v/v) solution of guinea pig complement in phosphate-buffered saline containing 50 micrograms/ml propidium iodide for 45 min at 39 degrees C. Then the blastocysts were transferred to ice-cold absolute ethanol containing 25 micrograms/ml bisbenzimide and evaluated under a fluorescence microscope. Since trophectoderm cells were permeabilised by antibody-mediated complement lysis, they were stained by propidium iodide (red or pink). Bisbenzimide can enter lysed and non-lysed cells and therefore stained also inner cell mass cells (blue) which had been protected from complement lysis by trophectoderm cells. This modified procedure proved to be very reliable for differential cell staining of bovine blastocysts produced under various culture conditions. A comparison of blastocysts produced in Ménézo's B2 vs. TCM 199 media (both supplemented with 10% serum from cows at oestrus) revealed significant (P < 0.01) differences in total cell numbers (119 +/- 24 vs. 84 +/- 10; mean +/- SD) and in the numbers of trophectoderm cells (79 +/- 19 vs. 57 +/- 8) and inner cells mass cells (40 +/- 7 vs. 26 +/- 5) between the two culture systems. The modified staining procedure presented here is a valuable tool for evaluating the quality of in vitro produced bovine blastocysts and for improving of culture conditions.

Reciprocal translocation in a case of canine basal cell carcinoma

A case of basal cell carcinoma in a 10-year-old spaniel dog was analysed cytogenetically. A reciprocal translocation t(10;35) was detectable.

Secretion of cumulus expansion-enabling factor (CEEF) in porcine follicles

The objective of this study was to find out whether porcine cumulus and mural granulosa cells can secrete cumulus expansion-enabling factor (CEEF). Culture drops of M-199 medium were conditioned with denuded porcine oocytes (1 oocyte/microliter), cumulus cells from oocytectomized complexes (1 OOX/microliter), pieces of mural granulosa isolated from preantral to preovulatory follicles (1000 cells/microliter), or oviductal cells (1000 cells/microliter) for 24 hr. The production of CEEF was assessed by the addition of mouse OOX and follicle-stimulating hormone (FSH) (1 microgram/ml) to microdrops of the conditioned medium. After 16-18 hr, expansion of the mouse OOX was scored on a scale of 0 to 4 by morphologic criteria. Mouse OOX did not expand in nonconditioned FSH-supplemented medium. Immature porcine oocytes produced +3 to +4 expansion of the mouse OOX. Granulosa cells isolated from preantral and early antral follicles and cumulus cells isolated from all states of follicle development constitutively secreted CEEF under in vitro conditions. Mural granulosa cells of small, medium, and preovulatory (PMSG) follicles also secreted CEEF in vitro; however, FSH or leutenizing hormone (LH) stimulation was essential for this secretion. Hormonally induced secretion of CEEF was accompanied by expansion of the mural granulosa itself. Granulosa cells isolated from follicles of gilts 20 hr after PMSG and human chorionic gonadotropin (hCG) administration did not produce CEEF and did not expand in response to FSH and LH in vitro. CEEF activity also was found in the follicular fluid of small antral follicles, was reduced in medium follicles, and was not detectable in PMSG-stimulated follicles. However, CEEF activity was reestablished in the follicular fluid of preovulatory follicles by hCG injection, conceivably due to increased production of CEEF by cumulus cells. We conclude that (1) porcine cumulus and mural granulosa cells are capable of CEEF production in vitro and (2) autocrine secretion of CEEF by cumulus cells is involved in regulation of porcine cumulus expansion both in vitro and in vivo.

Conservation of locus-specific microsatellite variability across species: a comparison of two Drosophila sibling species, D. melanogaster and D. simulans

Fifteen microsatellite loci were studied in Drosophila melanogaster and Drosophila simulans, two closely related sibling species which split 2-3.5 MYA. Within-species variances in repeat number were found to differ up to 1,000-fold among individual microsatellite loci. A significant correlation of log variances between both species indicated a locus-specific mutation rate of microsatellites. Hence, locus-specific effects are apparently among the major forces influencing microsatellite variation and deserve more consideration in microsatellite analysis.

Laparoscopic recovery of pronuclear-stage goat embryos

The oviducts of 16 Saanen does, superovulated with follicle-stimulating hormone (FSH) and synchronised with prostaglandin F2 alpha were flushed 75 to 86 hours after the injection of prostaglandin. The mean (sd) ovulation rate was 13.7 (3.9). The flushings were directed orthograde through a flexible intravenous catheter, which was introduced into the oviduct via the infundibulum. The flushing medium was recovered by a balloon-catheter, which was placed in the uterine lumen near the uterotubal junction. Five does were flushed unilaterally either because they had one blocked oviduct or because they had ovulated on only one ovary. The overall embryo recovery rate was 72 per cent. Nine weeks later 11 of the donor ewes were examined laparoscopically and no adhesions of the reproductive organs were observed. Eight of these does were synchronised with progestagen-vaginal sponges, superovulated with FSH and their oviducts were flushed again. Their mean ovulation rate was 16.0 (4.3) and 86 per cent of the embryos were recovered. The optimal time to obtain pronuclear stage embryos was 75 to 78 hours after the injection of prostaglandin. All the embryos recovered within this period were at the pronuclear stage whereas 28 per cent of those recovered one to six hours later were at the two- or four-cell stage.

Interactions of insulin-like growth factor (IGF)-II and growth hormone in vivo: circulating levels of IGF-I and IGF-binding proteins in transgenic mice

To study interactions between insulin-like growth factor-II (IGF-II) and growth hormone (GH) in vivo, we crossed hemizygous transgenic mice carrying phosphoenolpyruvate carboxykinase (PEPCK)-IGF-II fusion genes with hemizygous PEPCK-bovine GH (bGH) transgenic mice. Offspring harbouring both transgenes (IB), the IGF-II transgene (I) or the bGH transgene (B), and non-transgenic littermates (C) were obtained. Blood samples were taken before (end of week 12) and after (end of week 14) the mice had received a diet high in protein and low in carbohydrates to stimulate PEPCK promoter-controlled transgene expression. Mean serum GH concentrations of both B and IB mice corresponded to 900 ng/ml and increased more than twofold (P < 0.001) after 1 week of the high-protein diet. GH concentrations in controls and I mice were less than 20 ng/ml. Serum IGF-II concentrations in I and IB mice were three-to fourfold higher than those in C and B mice. Whereas IGF-II concentrations were not changed by the high-protein diet in the last two groups, serum IGF-II increased significantly in I (P < 0.001) and IB mice (P < 0.05). This increase was significantly (P < 0.05) less pronounced in IB than in C and I mice. Circulating IGF-I concentrations were about twofold (P < 0.001) higher in B and IB than in C and I mice, and showed a tendency to be lower in I than in C and in IB than in B mice when animals were maintained on the standard diet. The high-protein diet did not change circulating IGF-I concentrations in controls and B mice, but resulted in a significant reduction of serum IGF-I concentrations in I (P < 0.05) and IB mice (P < 0.001). Consequently, after PEPCK-IGF-II transgene expression was stimulated, serum IGF-I concentrations were significantly (P < 0.05) lower in I than in C and in IB than in B mice. Serum IGF-binding protein (IGFBP)-2 concentrations were significantly (P < 0.05) higher in I mice than in all other groups when mice were maintained on the standard diet, with a tendency to reduced IGFBP-2 concentrations in B mice. After the high-protein diet, serum IGFBP-2 concentrations did not change in C and I mice, but increased by two- to threefold in B and IB mice (P < 0.001). Serum IGFBP-3 concentrations tended to be greater in B and IB than in C and I mice, but these differences were mostly not significant. IGFBP-4 concentrations were significantly (P < 0.001) increased by GH overproduction in B and IB mice. Our data suggest that the reduction in circulating IGF-I concentrations by increased IGF-II is most probably due to the limited serum IGF binding capacity and the short half-life of free IGFs, rather than to a reduction in GH-dependent IGF-I production. Effects of GH overproduction on serum IGFBP-2 concentrations depend on dietary factors and may be both inhibitory and stimulatory.

Karyoplast-cytoplast volume ratio in bovine nuclear transfer embryos: effect on developmental potential

To evaluate the effect of karyoplast-cytoplast ratio on the development of nuclear transfer embryos, karyoplasts from day 4, day 5, and day 6 embryos were transferred to oocytes enucleated with different volumes of cytoplasm: Type 1, removal of a small volume of cytoplasm equivalent to the first polar body, Type 2, removal of a volume of cytoplasm approximately equal to the volume of the respective karyoplast, and Type 3, removal of half of the oocyte volume. In addition, the effect of experimental reduction of karyoplast cytoplasm was investigated in day 4 and day 5 karyoplasts. Intact day 4 karyoplasts fused to Type 3 cytoplasts did not support development to blastocysts, whereas these karyoplasts yielded blastocysts in combination with Type 1 (7%) and Type 2 cytoplasts (12%). After experimental reduction of cytoplasmic volume in day 4 karyoplasts, blastocysts (10%) were also obtained after fusion with Type 3 cytoplasts, probably due to reduction of cytoplasmic chimerism. With day 5 karyoplasts, blastocyst rate was higher in combination with Type 2 (34%) than with Type 1 (19%) and Type 3 cytoplasts (16%; P < 0.05). The use of day 6 intact karyoplasts resulted in a significantly (P < 0.05) higher proportion of blastocysts when fused with Type 2 (38%) or Type 1 cytoplasts (34%) than with Type 3 cytoplasts (16%). These results suggest that enucleation of oocytes with a volume similar to that of the respective karyoplast creates better conditions for cell cycle interactions with all types of karyoplasts than enucleation with minimal or large volume of cytoplasm.

Support for the development of bovine embryos in vitro by secretions of bovine trophoblastic vesicles derived in vitro

This study evaluated whether trophoblastic tissue derived in vitro secretes factors that support bovine embryonic development in vitro. The embryotrophic activity of these secretions was analysed in three different culture conditions based on TCM-199: (1) in a routine culture system using cumulus cells and 10% oestrous cow serum; (2) without cells but with 10% oestrous cow serum; and (3) under serum-free conditions. Rates of development to the 5-8-cell and blastocyst stages, as well as numbers of inner cell mass and trophectoderm cells of blastocysts were determined. In the absence of cumulus cells, cleavage rates of 5-8-cell embryos were significantly (P < 0.05) higher in trophoblastic vesicle-conditioned medium than in TCM-199 in both the presence (71% versus 49%) and absence (70% versus 49%) of serum. Trophoblastic vesicle-conditioned medium had a significant (P < 0.05) positive effect on the rate of development to the blastocyst stage when compared with TCM-199 in the presence of cumulus cells and serum (39% versus 33%), only serum (26% versus 19%), or in the absence of cells and serum (21% versus 5%). The numbers of inner cell mass and trophectoderm cells, and total number of cells in blastocysts produced in the cumulus cell coculture system in serum-free trophoblastic vesicle-conditioned medium or TCM-199 supplemented with serum were greater than those of blastocysts produced without cumulus cells or serum. Fractionation of serum-free trophoblastic vesicle-conditioned medium by ultrafiltration (10 kDa cut off) confined the embryotrophic activity mainly to the low molecular mass fraction. This study shows that serum-free trophoblastic vesicle-conditioned medium contains potent embryotrophic factors which act in a complementary manner to those secreted by cumulus cells and those supplemented with serum and result in reliably high blastocyst rates in the range of 40%. Since contamination of trophoblastic vesicle-conditioned medium with serum proteins can be avoided, this medium may be a reasonable source for the purification of specific embryotrophic factors.

Correlations between chemical parameters, mitogenic activity and embryotrophic activity of bovine oviduct-conditioned medium

To establish parameters predicting the quality of bovine oviduct epithelial cell-conditioned media, we compared media conditioned by oviduct cells from cows at Day 2 (n = 3) and Day 15 (n = 3) of the estrous cycle. In addition, we tested the influence of time of conditioning. Media were evaluated for their embryotrophic activity using a cumulus cell co-culture system as a control. The same media were tested for their mitogenic activity on NIH 3T3 cells and for chemical parameters, including total protein, and de novo synthesized protein as well as for concentrations of glucose, lactate and ammonium. Analysis of variance did not reveal a significant effect by stage of the estrous cycle on the embryotrophic activity of conditioned media. However, there was a significant effect by time of conditioning on the proportion of 5- to 8-cell embryos (P < 0.01) and of blastocysts and hatched blastocysts (P < 0.05). None of the conditioned media (19 to 31% blastocysts) was superior to the cumulus cell co-culture system (32% blastocysts). In the conditioned media, the proportion of 5- to 8-cell embryos correlated positively with mitogenic activity on 3T3 cells (r = 0.64; P < 0.05), whereas the proportion of blastocysts was not significantly correlated with this parameter. In summary, our results provide evidence for an effect of time of conditioning on embryotrophic activity of oviduct epithelial cell-conditioned media. The fact that mitogens for NIH 3T3 cells affect the proportion of 5- to 8-cell embryos but not of blastocysts suggests different culture requirements for early and late preimplantation stage development of bovine embryos.

Effect of insulin-like growth factor I (IGF-I) at high concentrations on blastocyst development of bovine embryos produced in vitro

This study was carried out to determine the effects of oestrous cow serum containing insulin-like growth factor I (IGF-I) and supplementation with recombinant IGF-I on subsequent development of bovine embryos produced in vitro. When culture medium was supplemented with oestrous cow serum containing 34.8 ng endogenous IGF-I ml-1, more embryos (P < 0.01) developed to blastocysts by day 9 and more blastocysts hatched on day 13 after insemination (P < 0.01) than in the control group. The effect of the addition of 10, 50 and 100 ng IGF-I ml-1 to culture media containing oestrous cow serum and granulosa cells was also evaluated. Supplementation with 10 ng IGF-I ml-1 did not improve embryo development at any stage. The addition of 50 and 100 ng IGF-I ml-1 did not affect development during the first three cell divisions. However, on day 7 these groups yielded a higher embryo rate than did the control group. Similarly, the proportion of blastocysts on day 9 was enhanced. The addition of 100 ng IGF-I ml-1 also increased the proportion of blastocysts. These data suggest that IGF-I at high concentrations accelerates the development to the blastocyst stage by shortening the transition from the morula to the blastocyst stage. The addition of 100 ng IGF-I ml-1 increased the proportion of hatched blastocysts on day 13. The addition of oestrous cow serum and IGF-I to TCM 199 free of granulosa cells did not increase the proportion of embryos on day 7. However, the progress to blastocysts and hatched blastocysts on days 9 and 13 was significantly lower (P < 0.05). The addition of IGF-I to culture medium without oestrous cow serum but with granulosa cells resulted in significantly lower embryo development than in the control group or in the group supplemented with oestrous cow serum and IGF-I (P < 0.01). The results support the hypothesis that culture media containing high concentrations of IGF-I combined with oestrous cow serum and granulosa cells can improve the development of embryos produced in vitro.