Morphologic and histologic comparisons between in vivo and nuclear transfer derived porcine embryos

Nuclear transfer (NT) is an inefficient but invaluable tool of the biotechnology industry. This study looked at abnormalities associated with peri-implantation NT porcine embryos. Four experimental groups were examined: nonpregnant animals, in vivo pregnant animals, NT recipients, and manipulation control embryos (MC). Embryos (Day 10, 12, or 14) were evaluated for embryonic disc diameter, gross morphology, nucleoli density, and mitotic figure index. Day 12 (P < or = 0.03) and Day 14 (P < or = 0.01) NT embryos had increased numbers of nucleoli, and Day 14 NT embryos had an increased (P < or = 0.03) mitotic index compared to in vivo and MC embryos. In vivo produced Day 14 embryos had increased (P < or = 0.01) disk diameters when compared to other embryos except for MC Day 14, which also showed increases (P < or = 0.01) in disk diameter except when compared to in vivo produced Day 12 and Day 14 embryos. In vivo produced Day 12 had greater (P < or = 0.03) disk diameters when compared to NT and MC embryos except for MC Day 14, and in vivo produced Day 14 embryos, which had a significantly increased (P < or = 0.01) disk diameter. In vivo produced Day 14 embryos were morphologically more advanced (P < or = 0.01) than Day 14 NT and MC counterparts. NT embryos develop at a slower rate than their in vivo produced counterparts. The increase in nucleoli and mitotic index of NT embryos suggest the cell cycle may be affected or the NT embryos are employing other means to compensate for slow development. The techniques used during NT also appear to compromise embryo development.

Centrosomal protein centrin is not detectable during early pre-implantation development but reappears during late blastocyst stage in porcine embryos

Centrin is an evolutionarily conserved 20 kDa, Ca+2-binding, calmodulin-related protein associated with centrioles and basal bodies of phylogenetically diverse eukaryotic cells. Earlier studies have shown that residual centrosomes of non-rodent mammalian spermatozoa retain centrin and, in theory, could contribute this protein for the reconstruction of the zygotic centrosome after fertilization. The present work shows that CEN2 and CEN3 mRNA were detected in germinal vesicle-stage (GV) oocytes, MII oocytes, and pre-implantation embryos from the two-cell through the blastocyst stage, but not in spermatozoa. Boar ejaculated spermatozoa possess centrin as revealed by immunofluorescence microscopy and western blotting. Immature, GV oocytes possess speckles of centrin particles in the perinuclear area, visualized by immunofluorescence microscopy and exhibit a 19 kDa band revealed by western blotting. Mature MII stage oocytes lacked centrin that could be detected by immunofluorescence or western blotting. The sperm centrin was lost in zygotes after in vitro fertilization. It was not detectable in embryos by immunofluorescence microscopy until the late blastocyst stage. Embryonic centrin first appeared as fine speckles in the perinuclear area of some interphase blastocyst cells and as putative centrosomes of the spindle poles of dividing cells. The cells of the hatched blastocysts developed centrin spots comparable with those of the cultured cells. Some blastomeres displayed undefined curved plate-like centrin-labeled structures. Anti-centrin antibody labeled interphase centrosomes of cultured pig embryonic fibroblast cells as distinct spots in the juxtanuclear area. Enucleated pig oocytes reconstructed by electrofusion with pig fibroblasts displayed centrin of the donor cell during the early stages of nuclear decondensation but became undetectable in the late pronuclear or cleavage stages. These observations suggest that porcine zygotes and pre-blastocyst embryonic cells lack centrin and do not retain exogenously incorporated centrin. The early embryonic centrosomes function without centrin. Centrin in the blastocyst stage embryos is likely a result of de novo synthesis at the onset of differentiation of the pluripotent blastomeres.

Production of endothelial nitric oxide synthase (eNOS) over-expressing piglets

Vascular function, vascular structure, and homeostasis are thought to be regulated in part by nitric oxide (NO) released by endothelial cell nitric oxide synthase (eNOS), and NO released by eNOS plays an important role in modulating metabolism of skeletal and cardiac muscle in health and disease. The pig is an optimal model for human diseases because of the large number of important similarities between the genomic, metabolic and cardiovascular systems of pigs and humans. To gain a better understanding of cardiovascular regulation by eNOS we produced pigs carrying an endogenous eNOS gene driven by a Tie-2 promoter and tagged with a V5 His tag. Nuclear transfer was conducted to create these animals and the effects of two different oocyte activation treatments and two different culture systems were examined. Donor cells were electrically fused to the recipient oocytes. Electrical fusion/activation (1 mM calcium in mannitol: Treatment 1) and electrical fusion (0.1 mM calcium in mannitol)/chemical activation (200 microM Thimerosal for 10 min followed by 8 mM DTT for 30 min: Treatment 2) were used. Embryos were surgically transferred to the oviducts of gilts that exhibited estrus on the day of fusion or the day of transfer. Two cloned transgenic piglets were born from Treatment 1 and low oxygen, and another two from Treatment 2 and normal oxygen. PCR, RT-PCR, Western blotting and immunohistochemistry confirmed that the pigs were transgenic, made message, made the fusion protein and that the fusion protein localized to the endothelial cells of placental vasculature from the conceptuses as did the endogenous eNOS. Thus both activation conditions and culture systems are compatible with development to term. These pigs will serve as the founders for a colony of miniature pigs that will help to elucidate the function of eNOS in regulating muscle metabolism and the cardiorespiratory system.

1 ABERRANT DNA METHYLATION IN PORCINE IN VITRO-, PARTHENOGENETIC-, AND NUCLEAR TRANSFER-PRODUCED BLASTOCYSTS

Aberrant DNA methylation of in vitro-, parthenogenetic-, and nuclear transfer-derived embryos has been implicated in the low developmental competence of early embryos. Demethylation of the genome occurs immediately after fertilization and continues through the blastocyst stage. Remethylation or reprogramming of the genome occurs around the time of implantation and is maintained in somatic tissues. The aim of this study was to analyze DNA methylation in porcine gametes and blastocysts. Differential DNA methylation hybridization was conducted to analyze the methylation status of the Bstu I site (CGCG) in the gamete and blastocyst epigenomes. Germinal vesicle oocytes were aspirated from ovaries collected at an abattoir, sperm was isolated from a fresh ejaculate, and blastocysts were derived and collected from in vivo, in vitro, nuclear transfer, and parthenogenetic sources. Genomic clones were selected from a porcine CpG Island library based on the presence of a Bstu I site. The inserts from these clones were PCR amplified and spotted on glass slides. DNA was digested with Mse I, ligated to linkers, and digested with Bstu I. Fragments with methylated Bstu I sites remained intact whereas fragments with unmethylated Bstu I sites were cut. Intact fragments were amplified by PCR and labeled with amino allyl-dUTP. Liver DNA served as the reference and was labeled with Cy5; the other samples were labeled with Cy3. An Axon Genepix 4000B scanner (Axon Instruments, Inc., Union City, CA, USA) was used to scan the slides. Initial analysis of the microarray image was performed with GenePix Pro 4.0 software. Additional analysis, performed by using Genespring 7.0 ANOVA (P < 0.05), identified 221 clones as being significantly different in at least one of the biological conditions of the gametes or the blastocysts. Forty-six clones were sequenced and BLAST analysis identified 18 clones that were unique, 16 clones that had no similarity, and 12 clones that had similarity to multiple genes. Ribosomal (RPS20, RPL18) and protoporphyrinogen oxidase (PPOX) genes were identified in several clones. Components of the immune system (CCRs, TLRs), a transcription factor (ATF2), and an embryo-specific gene (WNT8B) were also identified. A condition tree was created according to the standard correlation similarity measure for the spots identified as significantly different. The condition tree shows that the methylation profiles are most similar in the germinal vesicle oocyte, parthenogenetic blastocyst, nuclear transfer blastocyst, in vitro-produced blastocyst, and sperm. In vivo-produced blastocysts grouped separately from the other samples. These results are consistent with previous studies that have shown that gametes undergo demethylation after fertilization on through the blastocyst stage when the genome is remethylated. Additionally, these results suggest that the reprogramming events that occur during the development of the in vivo-produced blastocysts are less likely to occur in in vitro-, nuclear transfer-, and parthenogenetic-produced blastocysts. This work was funded by a grant from the NIH (RR13438) and Food for the 21st Century.

381 PRODUCTION OF A TRANSGENIC PIGLET BY A NEW SPERM INJECTION TECHNIQUE

The technique for intracytoplasmic sperm injection (ICSI) has, until now, focused on scoring the tail of the sperm prior to catching and aspiration into the injection pipette. This is in spite of the fact that damage to the head would more closely simulate what occurs during normal fertilization. In addition, to aid in visualizing the injection process so that a reduced volume can be injected, the oocyte is generally centrifuged to clear a portion of the cytoplasm. Thus, with conventional ICSI, the sperm are immobilized with polyvinylpyrrolidone, repeatedly frozen and thawed, treated with DTT or Triton X-100, and severed between the head and tail; the oocyte is centrifuged or activated. All of the above treatments are designed to compensate for the intrinsic defects in conventional ICSI. Our objective was to use a modified ICSI procedure whereby aggressively motile sperm were captured onto the broken tip of an injection pipette and then injected into noncentrifuged oocytes. Damage to the head of the sperm occurred on the pipette or while pushed through the zona pellucida. These procedures are based on the work of Yong et al. 2003 Hum. Reprod. 18, 2390, where they achieved an improvement in development in vitro as compared to conventional methods. Ovaries were collected from prepubertal gilts, and oocytes were aspirated and matured in vitro. Sperm were collected from a transgenic boar carrying the green fluorescent protein (GFP) and frozen. After thawing, aggressively motile sperm were captured and injected through the zona pellucida and into the cytoplasm of the in vitro-matured oocytes. A total of 452 injected oocytes (43-171 oocytes per recipient) were surgically transferred into the oviduct of six surrogate gilts. Two gilts (33%) became pregnant. One gave birth to a healthy male piglet. GFP expression was observed in the nose and hooves by direct epifluorescent examination of the newborn piglet. This pattern of GFP expression is identical to that in non-ICSI-derived GFP pigs in this line. This result showed for the first time that this new sperm injection technique could be used for production of a viable transgenic piglet using in vitro-matured oocytes and frozen-thawed sperm.

101 CRYOPRESERVATION OF PORCINE EMBRYOS DERIVED FROM SOMATIC CELL NUCLEAR TRANSFER

In the production of cloned pigs, a large number of nuclear transfer (NT) embryos generally need to be transferred into a single surrogate. Thus, attempts to conduct embryo transfer can be frustrating when either a synchronized surrogate is not available, or enough NT embryos are not produced. This problem would be solved if one could cryopreserve the porcine nuclear transfer embryos. Cryopreservation of porcine embryos has been successful only for in vivo-derived embryos. In vitro-derived porcine embryos are sensitive to chilling, and this sensitivity has been attributed to the lipid droplets in the cytoplasm. In previous reports, the viability of cyropreserved embryos was improved by removal of lipid drops from the cytoplasm. Therefore we designed a procedure to cryopreserve cloned blastocysts by a combination of the open pulled straw (OPS) vitrification method with removal of lipid drops from the oocyte. In vitro-matured MII oocytes were enucleated, and centrifuged (10 000 rpm, 5 min) to polarize the lipid droplets. This was followed by removal of the polarized lipid droplets and transfer of a donor fetal-derived fibroblast cell into the perivitelline space by micromanipulation. After electrical activation and fusion, the NT embryos were cultured in PZM-3 medium with 4 mg/mL BSA. Day 5 and Day 6 blastocysts (manipulation day was Day 0) were vitrified by equilibration with 25 mM HEPES-buffered TCM-199 containing 10% ethylene glycol, 10% DMSO, and 20% fetal calf serum for 2 min, followed by exposure to 20% ethylene glycol and 20% DMSO. Embryos were loaded into an OPS straw and immediately plunged into liquid nitrogen. The process from exposure of embryos to vitrification solution to plunging was 25–30 s. Embryos were thawed by immersing the end of the OPS straw in 0.3 M sucrose in which embryos were kept for 5 min, and then in 0.2 M sucrose for 5 min. Some embryos were cultured in PZM-3 for 12 h to determine the percentage and cell number of re-expanded blastocysts. The others were transferred to the uterus of a surrogate gilt within 3 h of thawing. Lipid removal appeared to have no harmful effect on embryo development and cell number of the blastocysts. Interestingly, a higher blastocyst percentage (28.8%, 178/619) was obtained with NT embryos from which the lipid had been removed as compared to normal NT (19.6%, 44/225; P < 0.01). The cell number (31.2 ± 7.7) of re-expanded blastocysts in the delipation group was comparable with normal NT blastocysts (33.6 ± 14.1, P = 0.33). The survival rate of blastocysts after freezing and thawing was enhanced after delipation (delipation group: 66.7%, 14/21; normal NT group: 21.9%, 9/42; P < 0.01). Two hundred and fourteen delipatized NT blastocysts were transferred to four surrogates after freezing and thawing. Three of the surrogates showed a delayed estrus cycle and one is still pregnant as confirmed by ultrasound scanning. We show that the combination of the OPS vitrification method with removal of lipid drops of oocyte cytoplasm might be an efficient way to cryopreserve porcine NT blastocysts. Funding for this project was from the NIH HL51670 and RR018877 and Food for the 21st Century.

Changes in the structure of nuclei after transfer to oocytes

Nuclear transfer and the potential for cloning animals have refocused attention on the oocyte. This focus is not limited to the use of the oocyte as a recipient in nuclear transfer procedures, but more broadly in terms of what factors are present in the oocyte that are responsible for establishing the developmental pattern of RNA synthesis and subsequent protein production. Deviations in the pattern of RNA synthesis can result in abortions, as well as abnormalities at birth. This paper will focus on the changes to nuclear structure that result from transfer to the cytoplasm of an oocyte, as well as some of the changes in the patterns of RNA synthesis that have been described.

Regression of NMU-induced mammary tumors with the combination of melatonin and 9-cis-retinoic acid

A significant increase in tumor regression was induced in N-nitroso-N-methylurea-induced mammary tumors in rats treated with the combination of melatonin and 9-cis-retinoic acid (9cRA). Treatment groups included: control (ethanolic saline), 9cRA (30 mg/kg chow/day), melatonin 500 microg/day, melatonin 1000 microg/day, melatonin 500 microg/day+9cRA and melatonin 1000 microg/day+9cRA. Rats treated with the lower dose of melatonin 500 microg+9cRA show the greatest degree of tumor regression (78%), with 54% undergoing complete regression and a significant increase in apoptotic cells observed by TUNEL Assay. Furthermore, tumor multiplicity and burden were significantly decreased by the combination of melatonin and 9cRA.

60 HISTOLOGICAL COMPARISONS BETWEEN NUCLEAR TRANSFER AND IN VIVO PORCINE EMBRYOS

Due to the high rate of embryonic loss during a nuclear transfer pregnancy, cloning is considered a relatively inefficient process. However, as the only method of producing knockout domestic animals it is considered an invaluable tool for the biotechnical industry. By histologically comparing embryos at significant stages in the porcine pregnancy (Days 10, 12, and 14), factors contributing to embryonic loss may be revealed. Many consider the period between days 10 and 14 to be critical for determining survivability as the embryos must undergo rapid changes to signal for maternal recognition of pregnancy as well as adapt to a changing environment. This study included three gilts per stage of pregnancy and four different experimental groups for each stage studied: nonpregnant animals, in vivo-pregnant animals, nuclear transfer (NT) recipients, and in vitro-manipulated recipients (IVM). IVM embryos were in vitro-produced embryos upon which a mock nuclear transfer has been performed in an effort to account for the variability introduced by the actual technique. Animals either were bred or underwent a surgical embryo transfer on Day 1 of the estrous cycle according to their assigned experimental group. Fifty embryos were transferred per embryo transfer. Embryos were flushed from the uterine horns at time of collection (Day 10, 12, or 14) and preserved in 10% neutral buffered formalin. All embryonic disc diameters and gross morphology were evaluated as parameters for normal development. Embryos were then dehydrated in ethanol, paraffin-imbedded, sectioned, stained with hemotoxylin and eosin, and Day 14 embryos were evaluated for abnormalities such as higher-than-normal nucleoli numbers, increased cytoplasmic vacuoles, and higher than normal numbers of mitotic figures. All results were analyzed using ANOVA. There were significant differences (P < .0001) between diameters of the embryonic disks, with the diameters of the NT embryonic disks being smaller than those of the in vivo controls at all stages studied. Morphologically, the in vivo controls were more developmentally competent than their NT counterparts by the time they reached Day 14 (P = 0.0002) in that most had achieved the more advanced elongated form of growth as opposed to remaining spherical in shape. Significant histological differences in the number of nucleoli per nuclei were also found between in vivo and NT embryos (P = 0.05) as well as between MNT and NT embryos (P = 0.05). Therefore, nuclear transfer embryos develop at a much slower rate than their in vivo counterparts and often exhibit histological abnormalities that could contribute to this slow growth. Due to the apparent increase in nucleoli, it is possible that NT embryos are being arrested at a specific stage in the cell cycle. The authors would like to acknowledge the Research Animal Diagnostic Laboratory for their help in imbedding, sectioning, and staining the embryos; Dr. Duane Keisler for running the hormone assays; and Kristin Whitworth, Melissa Samuel, Aaron Bonk, Jin-Geol Kim, Emily Fergason, David Wax, Tom Cantley, August Rieke, Randy Farrell, and Lacey Griesbaum for all their help.

38 HIGH OSMOLARITY AT EARLY CULTURE STAGE IMPROVES IN VITRO DEVELOPMENT OF PRE-IMPLANTATION PORCINE NUCLEAR TRANSFER EMBRYOS

Fragmentation occurs during early developmental stage of electrically activated oocytes and nuclear transfer (NT) embryos, and it might be the cause of the low developmental rate of pre-implantation porcine nuclear transfer embryos. The present study was conducted to investigate whether addition of sugars such as sorbitol and sucrose suppresses fragmentation and supports the development of NT embryos. Oocytes derived from a local abattoir were matured for 42–44 h and enucleated. Fetal fibroblast cells were obtained from a Day 35 porcine fetus. Parthenogenetically activated oocytes or NT embryos were cultured in PZM-3 for 6 days, or in PZM-3 supplemented with sorbitol or sucrose for 2 days and then cultured in PZM-3 for the remaining 4 days. The osmolarity of PZM-3, PZM-3 supplemented with 0.05 M or 0.1 M sorbitol, and PZM-3 with 0.05 M sucrose was 269 ± 6.31, 316 ± 3.13, 362 ± 4.37 and 315 ± 5.03 mOsm, respectively. When the parthogenotes were cultured in PZM-3 supplemented with 0.05 M sorbitol or sucrose for the first 2 days and then cultured in PZM-3 without sugar, a significantly higher (P < 0.05) cleavage rate and blastocyst rate was observed. Interestingly, sugar addition into PZM-3 at early culture stage for 2 days reduced the fragmentation rate compared to the rate in PZM-3 without sugar. In NT embryos, sugar addition into PZM-3 significantly (P < 0.05) increased the cleavage rate (67.6 ± 5.80 vs. 77.3 ± 3.03) and developmental rate to the blastocyst stage (10.2 ± 0.79 vs. 19.4 ± 1.77). There was no significant difference between treatments for the number of nuclei in the blastocysts. In addition the fragmentation rate in sugar-supplemented PZM-3 was reduced compared to that in PZM-3 without sugar (26.1 ± 4.30 vs. 14.5 ± 1.74). In conclusion, the increased osmolarity of PZM-3 with sugar supplementation at an early developmental stage for 48 h could increase the cleavage and developmental rate to the blastocyst stage by reducing the fragmentation rate.

43IMPROVED IN VITRO DEVELOPMENT OF PORCINE NUCLEAR TRANSFER EMBRYOS WITH 6-DMAP FOLLOWING FUSION

Although nuclear transfer (NT) has successfully produced cloned piglets, the development to blastocyst and to term is still low. Activation of the NT embryos is one of the key factors to improve the developmental ability of porcine NT embryos. Electric pulses as well as chemicals have been used to activate porcine NT embryos. This study was conducted to investigate the effect of continued activation following fusion pulses on in vitro development of porcine NT Embryos. Oocytes derived from a local abattoir were matured for 42 to 44h and enucleated. Ear skin cells were obtained from a 4-day-old transgenic pig transduced with eGFP recombinant retrovirus. Enucleated oocytes were reconstructed and cultured in PZM-3 in a gas atmosphere of 5% CO2 in air. Cleavage and blastocyst developmental rates were assessed under a stereomicroscope on Day 3 or 6. Blastocysts were stained with 5μg of Hoechst 33342 and total cell number was determined with an epifluorescent microscope. In Experiment 1, oocytes were activated with two 1.2kV/cm for 30μs (E) in 0.3M mannitol supplemented with either 0.1 or 1.0mM Ca2+. In each treatment, activated oocytes were divided into three groups. The first group was control (E). Other two groups were exposed to either ionomycin and 6-DMAP (E+I+D) or 6-DMAP (E+D) immediately after the electric pulses. In Experiment 2, fusion was conducted by using 1.0mM Ca2+ in the fusion medium. Fused NT embryos were divided into three treatments. NT embryos were fused and activated simultaneously with electric pulse as a control (C); the second group was treated with 6-DMAP immediately after fusion treatment (D0); and the third group was treated with 6-DMAP at 20min (D20) after fusion. In experiment 1, for 0.1mM Ca2+, developmental rates to the blastocyst stage for E, E+I+D or E+D were 12.5, 26.7 and 22.5%, respectively. For 1.0mM Ca2+, developmental rates to the blastocyst stage were 11.4, 28.3 and 35.6%, respectively. The activated oocytes treated with 6-DMAP following the electric pulses by using 1.0mM Ca2+ in fusion medium had higher (P&lt;0.05) developmental rates to the blastocyst stage. In Experiment 2, developmental rates to the blastocyst stage for C, D0 or D20 were 10.0, 12.3, and 19.9%, respectively. Developmental rate to the blastocyst stage was higher (P&lt;0.05) in D20. Fragmentation rates were 19.9, 10.8, and 9.0%, respectively. Regardless of Ca2+ concentration in fusion medium, continued treatments with chemicals following electric pulses supported more development of porcine activated oocytes. Treating NT embryos with 6-DMAP alone after fusion was completed by using 1.0mM Ca2+ in fusion medium improved the developmental rates to the blastocyst stage and prevented fragmentation accompanied by electric fusion. This study was supported by NIH NCRR 13438 and Food for the 21st Century.

318EFFECT OF PIG FOLLICLE FLUID AND FETAL CALF SERUM ON PORCINE OOCYTE MATURATION AND SUBSEQUENT DEVELOPMENT AFTER ACTIVATION AND SOMATIC CELL NUCLEAR TRANSFER

In vitro maturation of porcine oocytes is very important for understanding porcine somatic cell nuclear transfer (SCNT). In order to develop an in vitro maturation system that can provide more high quality oocytes, the effect of porcine follicle fluid (pFF) (gathered from 3–5-mm porcine follicles) and fetal calf serum (FCS: Sigma, St. Louis, MO, USA), as an important additional component of a chemically-defined medium was studied. Cumulus-oocyte complexes (COC) derived from follicles 3–5mm in diameter were cultured in three different media: a chemically-defined medium (CDM: TCM-199 with 0.1mgmL−1 cysteine, 10ngmL−1 EGF, 0.5μgmL−1 LH and 0.5μgmL−1 FSH); CDM with 10% pFF (CDM+p); and CDM with 10% FCS (CDM+F). After 42–44h of maturation, oocytes with a clear polar body were classified as matured oocytes. Matured oocytes stimulated by electric pulse (120v, 30μs, 2 pulse), or enucleated and fused with fibroblasts to construct SCNT embryos by using the same electrical parameters. All of these parthenogenetic and SCNT embryos were cultured in Porcine Zygote Medium-3. The blastocyst rate was assessed under a stereomicroscope on Day 6, and the number of nuclei in the blastocysts was counted under a fluorescent microscope after staining with 5μgmL−1 of Hoechst 33342. All data were subjected to a Generalized Linear Model Procedure (PROC-GLM) of Statistical Analysis System (SAS). The maturation rates of porcine oocytes in CDM and CDM+p were 53.2±3.8% (539/1050) and 69.7±3.8% (587/847), respectively;; in CDM and CDM+F, 61.1±3.1% (471/776) and 70.2±3.7% (577/844), respectively. Oocytes matured in CDM+p and CDM+F showed a higher (P&lt;0.05) maturation rate than those in CDM. The percentages of parthenogenetic blastocysts of oocytes matured in CDM and CDM+p were 13.9±2.1% (35/250) and 20.2±5.3% (64/300), and the numbers of nuclei in these blastocysts were 25.8±2.3 and 25.8±1.4, respectively. The blastocyst rate from CDM- and CDM+F-matured oocytes were 20.1±2.0% (53/272) and 22.2±4.7%(71/298), and the numbers of nuclei in these blastocysts were 24.7±1.5 and 25.3±1.5, respectively. There were no significant (P&gt;0.05) differences in the percentages of parthenogenetic blastocysts and nuclei numbers between CDM and CDM+p, or CDM and CDM+F. The percentages of blastocysts in SCNT embryos derived from CDM and CDM+p were 8.1±1.5% (14/192) and 12.3±1.9% (24/192), while the nuclei numbers in these blastocysts were 26.6±1.2 and 34.5±2.2, respectively. The percentages of blastocysts after SCNT from oocytes matured in CDM and CDM+F were 24.3±4.9% (35/139) and 27.1±5.5% (45/176), while the numbers of nuclei were 29.8±2.5 and 32.2±1.9, respectively. There were no significant (P&gt;0.05) differences between CDM and CDM+p, or CDM and CDM+F in SCNT embryo blastocyst rate, but the SCNT embryos derived from CDM+p showed a higher (P&lt;0.05) nuclear number. In conclusion, these results indicate that 10% pFF or FCS in CDM can promote a higher maturation rate of porcine oocytes. As recipient cytoplasm for SCNT, oocytes matured in CDM+p can support development of blastocysts that contain more nuclei than those matured in CDM alone. Supported in part by Food for the 21st Century and RR13438.

75HIGHLY EFFICIENT AND RELIABLE CHEMICALLY ASSISTED ENUCLEATION METHOD FOR HANDMADE CLONING IN CATTLE AND SWINE

In bovine and porcine nuclear transfer, most traditional enucleation procedures require potentially harmful chromatin staining and UV illumination. The purpose of our work was to find an efficient and reliable chemically-assisted procedure for enucleation connected to the handmade cloning (HMC) technique without chromatin staining. Slaughterhouse-derived oocytes were collected and matured in vitro. At 21 (bovine) or 43 (porcine) h after the start of maturation, cumulus cells were removed with vortexing and oocytes were further incubated in the maturation medium supplemented with 0.5μgmL−1 demecolcine for 2h. Subsequently, zonae pellucidae were digested with 2mgmL−1 pronase in the presence of 10% cattle serum (CS) for 6 to 8min and washed in HEPES-buffered TCM-199 medium and 20% CS. Bisection was performed in the same medium by hand under a stereomicroscope by using a microblade. A small membrane protrusion observable on the surface of oocytes was used as an orientation point. One-third of the cytoplasm connected to this protrusion was removed, and the cytoplasts and karyoplasts were collected separately. Bovine cytoplasts were used as recipients for HMC experiments (Vajta et al., 2003, Biol. Reprod. 68, 571–578) with fetal fibroblasts as donors, and reconstructed embryos were cultured for 7 days. In Experiment 1 (3 replicates), the possibility of oriented bisection at different time points was determined on a total of 225 bovine oocytes. At 5, 15, 25, 35 and 55min after the end of pronase digestion 64, 91, 93, 72 and 59% of oocytes had membrane protrusions (P&lt;0.05 between all groups, SAS Genmod) illustrating the time-dependent manner of the protrusion. In Experiment 2, the efficiency and reliability of enucleation was measured. Bisection was performed between 5 and 35min after pronase digestion. Subsequently both supposed cytoplasts and karyoplasts were stained with Hoechst and investigated under UV light. In cattle (9 replicates), bisection was successfully performed in 94% (519/552) of oocytes, and 98% (507/517) of those bisected were enucleated, i.e. the chromatin was entirely in the presumptive karyoplast. In swine (3 replicates), 91% (302/331) of oocytes were successfully bisected and 95% (280/296) were enucleated. In Experiment 3 (cattle; 4 replicates), blastocyst per reconstructed embryo rates were 47% (139/293), illustrating the high developmental ability in vitro. Considering that no oocyte selection based on the presence of polar body was performed, the above system seems to be more efficient and reliable than other enucleation methods. Moreover, expensive equipment (inverted fluorescent microscope) and a potentially harmful step (staining and UV illumination) can be eliminated from the HMC without compromising the high in vitro efficiency.

Overexpression of the MT1 melatonin receptor in MCF-7 human breast cancer cells inhibits mammary tumor formation in nude mice

Overexpression of the MT1 melatonin receptor in MCF-7 human breast cancer cells significantly enhances the response of these cells to the growth-inhibitory actions of melatonin. Athymic nude mice implanted with MT1-overexpressing MCF-7 cells developed significantly fewer palpable tumors (60% reduction) compared to mice receiving vector-transfected MCF-7 cells (vt-MCF-7). In response to exogenous melatonin, tumor incidence in the mice receiving the MT1-overexpressing MCF-7 cells was decreased by 80% compared to mice receiving vt-MCF-7 cells. Interestingly, daily melatonin administration did not decrease tumor incidence in mice receiving vt-MCF-7 cells, but rather stimulated overall tumor formation.

Transgenic swine for biomedicine and agriculture

Initial technologies for creating transgenic swine only permitted random integration of the construct. However, by combining the technology for homologous recombination in fetal somatic cells with that of nuclear transfer (NT), it is now possible to create specific modifications to the swine genome. The first such example is that of knocking out a gene that is responsible for hyperacute rejection (HAR) when organs from swine are transferred to primates. Because swine are widely used as models of human diseases, there are opportunities for genetic modification to alter these models or to create additional models of human disease. Unfortunately, some of the offspring resulting from NT have abnormal phenotypes. However, it appears that these abnormal phenotypes are a result of epigenetic modifications and, thus, are not transmitted to the offspring of the clones. Although the technique of producing animals with specific genetic modifications by NT has been achieved, improvements to the NT technique as well as improvements in the culture conditions for somatic cells and the techniques for genetic modification are still needed.

Beta-turn formation by a six-residue linear peptide in solution

A model peptide AAGDYY-NH2 (B1), which is found to adopt a beta-turn conformation in the TEM-1 beta-lactamase inhibitor protein (BLIP) in the TEM-1/BLIP co-crystal, was synthesized to elucidate the mechanism of its beta-turn formation and stability. Its structural preferences in solution were comprehensively characterized using CD, FT-IR and 1H NMR spectroscopy, respectively. The set of observed diagnostic NOEs, the restrained molecular dynamics simulation, CD and FT-IR spectroscopy confirmed the formation of a beta-turn in solution by the model peptide. The dihedral angles [(phi3, phi3) (phi4, phi4)] of [(-52 degrees, -32 degrees ) (-38 degrees, -44 degrees )] of Gly-Asp fragment in the model peptide are consistent with those of a type III beta-turn. In a conclusion, the conformational preference of the linear hexapeptide B1 in solution was determined, and it would provide a simple template to study the mechanism of beta-turn formation and stability.

Involvement of the mt1 melatonin receptor in human breast cancer

Two putative melatonin receptors have been described including the cell surface G-protein-linked receptors, mt1 and MT2, and the nuclear retinoic orphan receptor alpha (RORalpha). The mt1 receptor, but not the MT2 receptor, is expressed in human breast tumor cell lines, and melatonin-induced growth suppression can be mimicked by the mt1 and MT2 agonist, AMMTC, and blocked by the antagonist, CBPT. RORalpha receptors are also expressed in MCF-7 breast cancer cells and the putative RORalpha agonist CPG-52608 inhibits MCF-7 cell growth but with a very different dose-response than melatonin. Finally, melatonin and AMMTC, but not CPG-52608, can repress RORalpha transcriptional activity in MCF-7 cells.

Tumor prevention by 9-cis-retinoic acid in the N-nitroso-N-methylurea model of mammary carcinogenesis is potentiated by the pineal hormone melatonin

Our laboratory has demonstrated that treatment of MCF-7 breast cancer cells with melatonin (Mlt) followed 24h later with physiological concentrations of all-trans retinoic acid (atRA) results in apoptosis. These studies were extended into trials using the N-nitroso-N-methylurea (NMU)-induced rat mammary tumor model. Initial studies conducted by feeding the animals 9-cis-retinoic acid (9cRA in the chow) and administering melatonin by subcutaneous injection in the late afternoon demonstrated that the combination of Mlt and 9cRA was able to significantly prevent tumor development, and that the combination was more efficacious that either Mlt or 9cRA alone. In this report, we conducted studies to determine if lower doses of 9cRA could be used in combination with Mlt while still maintaining anti-tumor activity and if the route of administration of 9cRA (bolus (gavage) v.s. chronic (chow) routes) affected its interaction with Mlt. The studies presented here demonstrate that significantly reduced doses of 9cRA can be used in combination with Mlt while maintaining anti-tumor efficacy. Furthermore, our studies demonstrate that 9cRA is equally effective when it is administered chronically (chow) or as a bolus (gavage). These data demonstrate that the combined use of Mlt and 9cRA produces additive or synergistic effects, which are more efficacious than 9cRA alone. This combination of Mlt and 9cRA could be a potentially useful clinical treatment regimen for breast cancer since it allows the use of lower doses of retinoic acid, thus, avoiding the toxic side effects associated with the use of high dose retinoids.

Radioimmunotherapy for model B cell malignancies using 90Y-labeled anti-CD19 and anti-CD20 monoclonal antibodies

In recent years, radioimmunotherapy (RIT) with beta(-) particle emitting radionuclides targeting the CD20 antigen on B cells in the treatment of non-Hodgkin's lymphoma has provided the most compelling human clinical data for the success of RIT. CD19, like CD20, is an antigen expressed on the surface of cells of the B lineage, and CD19 may provide an alternative target for radioimmunotherapy of B cell neoplasms. CD19 has been largely overlooked as a target for conventional 131I RIT, because the antigen rapidly internalizes upon binding of antibody, resulting in catabolism and significant release of 131I. Such modulation may be an advantage to RIT with radiometals such as 90Y, 177Lu, 213Bi and 225Ac. Herein, we have compared beta(-) particle RIT with antibodies targeting either CD19 or CD20. The anti-CD19 and anti-CD20 antibodies, B4 or C2B8, respectively, were appended with the SCN-CHX-A''-DTPA bifunctional chelating agent and labeled with 90Y. In the tumor model used, there were three times as many CD20 target sites on lymphoma cells as compared to CD19 sites (62000 vs 20000 binding sites, respectively). We compared the efficacy of the 90Y-labeled antibodies to reduce lymphoma in a nude mouse xenograft solid tumor model, after measurable lymphoma appeared. Reduction in tumor size began at day 3 in all three 90Y-treated groups, but tumor began to recur in many animals 9 days after the treatments. There was one cure in each specific treatment group. In contrast, the tumor in the two control groups showed no regression. There was a significant prolongation of median survival time from xenograft (P < 0.0001) in all the 90Y-labeled antibody construct-treated groups (32 days for 0.15 mCi 90Y-B4; 26 days for 0.20 mCi 90Y-C2B8, and 23 days for 0.15 mCi 90Y-C2B8) in comparison to the two control groups (11 days for 0.02 mg of C2B8 and 9 days for untreated growth controls). Specificity of the radioimmunotherapy was also shown. In conclusion, 90Y-labeled anti-CD19 antibody has efficacy comparable to 90Y-labeled anti-CD20 antibody in the treatment of mice bearing human lymphoma xenografts. These data suggest that CD19-targeted RIT merits further study.

Moloney murine leukemia virus integrase protein augments viral DNA synthesis in infected cells

Mutations in the IN domain of retroviral DNA may affect multiple steps of the virus life cycle, suggesting that the IN protein may have other functions in addition to its integration function. We previously reported that the human immunodeficiency virus type 1 IN protein is required for efficient viral DNA synthesis and that this function requires specific interaction with other viral components but not enzyme (integration) activity. In this report, we characterized the structure and function of the Moloney murine leukemia virus (MLV) IN protein in viral DNA synthesis. Using an MLV vector containing green fluorescent protein as a sensitive reporter for virus infection, we found that mutations in either the catalytic triad (D184A) or the HHCC motif (H61A) reduced infectivity by approximately 1,000-fold. Mutations that deleted the entire IN (DeltaIN) or 34 C-terminal amino acid residues (Delta34) were more severely defective, with infectivity levels consistently reduced by 10,000-fold. Immunoblot analysis indicated that these mutants were similar to wild-type MLV with respect to virion production and proteolytic processing of the Gag and Pol precursor proteins. Using semiquantitative PCR to analyze viral cDNA synthesis in infected cells, we found the Delta34 and DeltaIN mutants to be markedly impaired while the D184A and H61A mutants synthesized cDNA at levels similar to the wild type. The DNA synthesis defect was rescued by complementing the Delta34 and DeltaIN mutants in trans with either wild-type IN or the D184A mutant IN, provided as a Gag-IN fusion protein. However, the DNA synthesis defect of DeltaIN mutant virions could not be complemented with the Delta34 IN mutant. Taken together, these analyses strongly suggested that the MLV IN protein itself is required for efficient viral DNA synthesis and that this function may be conserved among other retroviruses.

An isothermal titration calorimetric method to determine the kinetic parameters of enzyme catalytic reaction by employing the product inhibition as probe

An isothermal titration calorimetric (ITC) method was developed to measure the kinetic parameters of ribonuclease A catalytic hydrolysis of cytidine 2',3'-cyclic monophosphate. Employing the inhibition of product as a probe, the K(m), K(i), k(c), and DeltaH(m) can be determined by two simple calorimetric measurements. First, the substrate was titrated into the cell containing high concentration of enzyme. The molar reaction heat was calculated from the titration peak area divided by substrate moles per titration, and the initial catalytic reaction rate in the presence of various concentrations of product can be calculated from the peak height and the molar reaction heat. From Michaelis-Menten function in the presence of inhibitors, the relationship between K(m) and K(i) can be obtained. Then, the dissociation constant, which is equal to K(i), was measured by a regular ITC experiment. Thus, K(m) and k(c) can be calculated. The method developed here can be applied in other enzyme catalytic systems with inhibitive products.