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Biomedical subjects

G B Anderson

Publications and source records attributed to G B Anderson.

At least 73 records · Page 4Linked to original sources
PubMed1993

Microinjection of bovine embryos with a foreign gene and its detection at the blastocyst stage.

This study was designed to measure the survival and development of pronuclear stage bovine zygotes after microinjection with DNA and either culture in vitro or incubation in the sheep oviduct and to determine the percentage of embryos that retain exogenous DNA at the blastocyst stage. In vitro matured and fertilized oocytes were examined for pronuclear development 18 to 20 h after coincubation with sperm. An ovine somatotropin gene construct was microinjected into ova with visible pronuclei. Microinjected ova and unmanipulated ova from the same in vitro derived pool were cocultured with oviductal epithelial cells or incubated in the sheep oviduct and cocultured, respectively, for 7 d. Blastocysts were subjected to polymerase chain reaction analysis for detection of exogenous DNA. The percentage of cleaved embryos that formed blastocysts was similar for microinjected and unmanipulated cultured ova. The percentage of blastocysts recovered from the sheep oviduct that hatched was higher than for blastocysts that developed in coculture. Fourteen of 26 (54%) blastocysts that developed from microinjected ova were positive for the exogenous DNA by polymerase chain reaction. The implications are discussed for polymerase chain reaction detection of the exogenous gene construct in a relatively high proportion of microinjected blastocysts.

Animals↗
PubMed1992

Inter- and intraspecific placentae in sheep, goats and sheep-goat chimaeras.

These studies compared inter- and intraspecific placentae during implantation and at full-term in sheep, goats and interspecific sheep-goat chimaeras. Histological sections prepared from intra- and interspecific day-26, 32 and 36 placentae in ewes and does indicated an altered ability of the trophoblast to invade the maternal caruncle in interspecific pregnancies. Two sheep-in-goat pregnancies were less, and two goat-in-sheep pregnancies were more, invasive than homologous pregnancies. Caprine pregnancies in chimaeras generally terminated before timed samples could be obtained, but biopsy samples collected at laparotomy between days 42 and 48 demonstrated both normal and abnormal placentation in chimaeras after breedings to rams. In six of 11 full-term fetal placentae from ovine pregnancies in chimaeras, there was abnormal retention of maternal caruncular tissue to the extent that macroscopic lesions were visible on the surface of the fetal cotyledons. Histological observations indicated that proliferation of maternal septa and hyalinization of maternal vessels had occurred at the expense of the fetal villi. Overall, the results suggested that the physiological events that regulate implantation are different in the two species, despite anatomical similarities between the ovine and caprine placenta. The caprine conceptus is likely to be rejected in the ovine or chimaeric uterus because of its over-invasiveness in the early stages of implantation, whereas the ovine conceptus can survive in the potentially chimaeric uterus.

Animals↗
PubMed1992

Superovulation of cattle with equine pituitary extract and porcine ESH.

Superovulation has been practiced in cattle for more than 50 years but the results have been highly variable. Scientists at six locations compared a horse pituitary extract (HAP) with a single batch of porcine FSH (pFSH) to determine the efficacy of these hormones to induce superovulation and to test for variability in the superovulatory response. Acetone-dried equine pituitaries were suspended in 40% ethanol containing 6% ammonium acetate, and the supernatant was mixed with 2.5 volumes of cold ethanol. The resulting precipitate was washed with cold ether and dried. Total doses of 18 mg of HAP and 36 mg of pFSH were injected intramuscularly (i.m.) over 4 days, two injections per day, and prostaglandin (PGF(2)alpha; 25 mg, i.m.) was administered on Day 3. Injections were begun on Days 6 to 13 of the estrous cycle. The overall ovulation rates (mean +/- SEM) for HAP and FSH were 8.8 +/- 0.7 and 15.1 +/- 1.0, respectively (n=231; P<0.01). Location interacted (P<0.01) with the type of gonadotropin for the ovulation rate. When expressed as a proportion of the number of corpora lutea, the total number of embryos recovered was greater (P=0.03) for pFSH than for HAP, but there was no difference in the number of Quality 1 and 2 embryos. The results show that HAP can induce a satisfactory superovulatory response, but there was no evidence of reduced variability of response to HAP compared with pFSH.

Journal Article↗
PubMed1992

Development of in vitro fertilized oocytes from pregnant and nonpregnant cows in oviductal epithelial and cumulus cell co-culture systems.

The objectives of this study were 1) to measure cleavage, blastocyst formation, and blastocyst hatching after in vitro maturation (IVM), fertilization (IVF) and culture (IVC) of oocytes aspirated from pregnant versus nonpregnant cows, and 2) to compare embryo development in co-culture with bovine oviductal epithelial cells versus cumulus cells. No differences in cleavage (38 versus 40%), blastocyst formation (13 versus 13%), or blastocyst hatching (53 versus 51%) were observed for in vitro-matured, fertilized, and cultured oocytes from pregnant versus nonpregnant cows, respectively (P>0.05), indicating that nonpregnant and early-pregnant cows are equally acceptable donors of oocytes for IVM/IVF/IVC procedures. Cleavage (36 versus 40%), blastocyst formation (11 versus 12%), and blastocyst hatching (50 versus 55%) were not different for embryos co-cultured with oviductal epithelial cells versus cumulus cells (P>0.05). Thus, equivalent embryo development can be obtained with co-culture systems commonly used for in vitro-derived bovine embryos. These results help to define variables that affect comparison of results across laboratories and that are relevant to the practical application of IVM/IVF/IVC procedures to cattle.

Journal Article↗
PubMed1992

Micromanipulation of mammalian embryos: Principles, progress and future possibilities.

Numerous advances in development of techniques for manipulating mammalian embryos outside the maternal environment have been made over the past decade. Some techniques were developed primarily for use in research; others were developed in response to problems of practical livestock production but have proven useful in research as well. Embryo micromanipulation procedures are used often in conjunction with embryo transfer, and interest in these procedures was stimulated by growth of the embryo transfer industry. Included in this review are discussions of procedures for manipulation of gametes and embryos, including sperm injection into oocytes, pronuclear and nuclear transfer, embryo biopsy and splitting, experimental chimera production and isolation of embryonic stem cells.

Journal Article↗
PubMed1992

Maternal serum reactivity to species-specific antigens in sheep-goat interspecific pregnancy.

Three models were used to test the hypothesis that interspecific pregnancy failure between the sheep and goat is due to a species-specific, maternal antibody response. Interspecific pregnancies were established in ewes and does, sheep in equilibrium goat chimeric conceptuses produced by injection of ovine blastocysts were transferred to ovine recipients, and ovine and caprine pregnancies were established in interspecific chimeras. Complement-mediated lymphocytotoxic and hemolytic assays were used to monitor onset and titer of antibodies. Sera from 3 of 8 injection-chimera recipients reacted with all caprine peripheral blood lymphocytes (PBL) and red blood cells (RBC) tested (n = 18). Sera from 3 of 6 ewes and 7 of 7 does also were pancytotoxic to PBL of the other species (n greater than or equal to 20). Absorptions with xenogeneic RBC generally removed the reactivity. The data were consistent with responses to species-specific, monomorphic antigens expressed on PBL and RBC, and probably trophoblast. The response preceded or coincided with interspecific pregnancy failure in does, but not in ewes. Accordingly, no xenoreactivity was observed in chimera sera but caprine pregnancies were resorbed (n = 16) and ovine pregnancies developed to term (n = 11). The data did not support the hypothesis that failure of caprine pregnancy in ewes or chimeras is due to a species-specific, maternal antibody response. In contrast, a maternal, cytotoxic antibody response to species-specific antigen(s) may contribute to failure of hybrid or ovine pregnancy in does.

Animals↗
PubMed1991

Preliminary observations on reproduction in a female sheep-goat chimaera.

Four oestrous cycles of a female sheep-goat chimaera were monitored by using a vasectomised ram. The mean (+/- se) length of the cycle was 18.5 +/- 0.64 days with a range from 17 to 20 days. The chimaera was superovulated twice, bred to fertile rams, and the embryos recovered by laparotomy 13 or five days after oestrus, so that karyotype analysis could reveal the genotype of the oocyte. After the first superovulation one ovine day-13 embryo was collected; two fragments of another embryo (or embryos) were also collected, but readable chromosome spreads were not obtained from these embryos or from the two four-cell embryos that were collected five days after the second superovulation. Two surgical embryo transfers to the chimaera resulted in pregnancies. The first transfer involved an eight-cell ovine embryo and two caprine morulae and ended in the abortion of an ovine fetus between days 110 and 130. The second pregnancy occurred after the transfer of two ovine and two caprine morulae. A healthy lamb was born on day 147 of pregnancy. Both placentae had small numbers of cotyledons. A histological evaluation of the cotyledons revealed an abnormal placentome structure in the first pregnancy but not in the second.

Animals↗
PubMed1991

Periodontal healing following guided tissue regeneration with citric acid and fibronectin application.

This study was undertaken to determine the effects of guided tissue regeneration (GTR) with and without citric acid conditioning and autologous fibronectin application. The study subjects were four female beagle dogs with spontaneous periodontitis. The dogs were given thorough root debridement and 4 weeks later, mucoperiosteal flaps were raised on both sides of the mandible involving the 2nd, 3rd, and 4th premolar and 1st molar teeth. After debridement, notches were placed on the roots at the level of supporting bone. Citric acid (pH 1) was topically applied for 3 minutes on the exposed root surfaces of one side (experimental). The roots were irrigated with normal saline solution. Both the root surfaces and the inner surface of the flap were then bathed in autologous fibronectin in saline. Following this, Gore-Tex periodontal material was adapted to the roots of each tooth and sutured. The contralateral side, serving as control, was treated by surgery and application of Gore-Tex periodontal material only. All membranes were removed 1 month after surgery, and the dogs sacrificed at 3 months. Both mesio-distal and bucco-lingual microscopic histological sections were evaluated by descriptive histology, and linear measurements and surface area determination of the furcal tissues were made. Periodontal healing following the use of GTR procedure resulted in an increase in connective tissue and alveolar bone regeneration. Adjunctive critic acid plus autologous fibronectin produced slightly better results, but these differences were not statistically significant for this sample.

Acid Etching, Dental↗
PubMed1991

Correlation of periodontal probe penetration and degree of inflammation.

This histological study correlated the depth of probe penetration to periodontal health in mongrel dogs. Various probing forces were also applied with an electronic pressure-sensitive probe and compared to manual probing. Three adult mongrel dogs with naturally occurring periodontitis in at least one quadrant were selected and gross scaling was only performed in these diseased areas. Mild gingivitis was diagnosed in other areas. One half was scaled and placed on a plaque control regimen to restore clinical health, while the other half remained untreated to maintain the existing gingivitis. The Gingival Index (GI) was recorded on 24 teeth achieving equal representation of different GI values. Probe tips were inserted utilizing manual pressure as well pressures of 15 and 25 gm directed with an electronic pressure-sensitive probe. The probes were bonded to the teeth, and the specimens were sacrificed. Blocks with the probes in place were fixed and decalcified. The probes were removed prior to processing. Sections from each probing site were microscopically analyzed, and the distance was recorded from the tip of the probe to the apical termination of the junctional epithelium (ATJE). The number of inflammatory cells was documented for two fields at x200, one coronal (X) and one apical (Y) to the penetration of the probe's tip. The data were analyzed by two-sample t-test and Pearson product-moment correlation coefficient. A strong correlation was established between probe penetration and degree of inflammation, X (r = 0.6936) and Y (r = 0.7075). The difference in mean inflammation scores between probes coronal or apical to the epithelium was highly significant (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Influence of feeder layer type on the efficiency of isolation of porcine embryo-derived cell lines.

Experiments were conducted to determine the effects of feeder layers composed of different cell types on the efficiency of isolation and the behavior of porcine embryo-derived cell lines. Inner cell masses (ICM) isolated from 7- to 8-d-old embryos were plated on feeder layers composed of Buffalo rat liver cells (BRL), a continuous cell line of murine embryonic fibroblasts (STO), STO combined with BRL at a 9:1 and 1:1 ratio, STO with BRL-conditioned medium (STO + CM), porcine embryonic fibroblasts (PEF), PEF combined with BRL at a 9:1 and 1:1 ratio, porcine uterine epithelial cells (PUE), murine embryonic fibroblasts (MEF), or an epithelial-like porcine embryo-derived cell line (PH3A). It was found that embryo-derived cell lines could be isolated only from the STO and the STO with BRL-conditioned medium treatments. The isolated cell lines were of epithelial-like and embryonic stem cell-like (ES-like) morphology. The feeders tested had an effect on the behavior of plated ICM. Some feeders, represented by PUE, BRL, STO:BRL (1:1), PEF:BRL (1:1), and PH3A, did not promote attachment of the ICM to the feeder layer; others, represented by STO and MEF, allowed attachment, differentiation and proliferation. On PEF feeders the ICM spread onto the feeder layer after attachment without apparent signs of proliferation or differentiation. None of the feeders tested increased the efficiency of isolation or the growth characteristics of embryo-derived (both ES-like and epithelial-like) cell lines over that of STO feeders.

Journal Article↗
PubMed1990

On the isolation of embryonic stem cells: Comparative behavior of murine, porcine and ovine embryos.

The efficiency of isolation and the characteristics of embryo-derived cell lines from murine, porcine, and ovine embryos cultured on STO feeders or homologous embryonic fibroblasts (HEF) feeders were compared. While murine isolated ICM or intact embryos plated on STO or HEF feeders gave rise to cell lines with embryonic stem cell-like (ES-like) morphology, ovine embryos did not. Cell lines with ES-like morphology were isolated from porcine intact embryos and isolated ICM when plated on STO feeders but not when plated on HEF. Neither murine nor porcine ES-like cell lines expressed cytokeratin 18 or vimentin. Unlike murine ES-like cell lines, porcine ES-like cells did not undergo observable differentiation in vitro or in vivo. Cell lines with epithelial-like morphology were isolated from porcine and ovine embryos. Both porcine and ovine epithelial-like cell kines expressed cytokeratin 18. When induced to differentiate in vitro, porcine and ovine epithelial-like cell lines formed vesicular structures. Electron microscopy revealed that the porcine vesicles were composed of polarized epithelial cells, each with a basally-located nucleus and an apical border containing numerous microvilli with a well organized microfilament core. The results of this study show that conditions which allow isolation of ES cells from murine embryos allow the isolation of porcine embryo-derived cell lines sharing some, but not all, the characteristics of murine ES cells.

Journal Article↗
PubMed1990

Embryo-transfer twinning and performance efficiency in beef production.

Effects of twinning on efficiency of beef production were estimated from results of bilateral transfer of two Angus x Hereford (AxH) embryos into each of 241 heifers and 84 cows (H, A, HxA or Holstein x H) over 4 yr. Calves were weaned at 180 d and fed either 220 d in a feedlot (1977) or 170 d on forage and 140 d in a feedlot (1978 to 1980). Effects of parity, twinning and sex of calf were estimated as covariates within year-breed of dam. Pregnancy at 45 to 60 d of gestation was 68% in heifers (H) and 74% in cows (C), with 40% single (S) and 60% twin (T) births. Dystocia was 28% in H vs 10% in C (P less than .05), and tended to be less (P greater than .05) for T than S in H. More placentas were retained (P less than .05) for T than for S in both H (35 vs 12%) and C (24 vs 4%). Twin gestations averaged 3 d shorter and subsequent calving intervals 13 d longer (P less than .05), but total calf mortality was slightly higher (P greater than .05). Abortions were 4% in H only. Twinning females lost maternal weight during late gestation (P less than .05) when crowding limited voluntary feed intake, while fetal requirements were 60% higher (P less than .01). Twins increased milk output 25% (P less than .05), but 11% higher feed intake maintained cow weight during lactation. Twinning reduced birth weight 13% and weaning weight 17% (P less than .05), but 400-d feedlot weight only 9% because of compensating feedlot gain. Twins gained 18% faster than S during postweaning 170-d forage feeding, but 5% slower in feedlot to 8% lighter 490-d weight (P less than .05). Assuming 40% higher veterinary and labor costs for twins, estimated integrated herd costs per unit of age-constant output value would be lower for T than for S production by about 24% for marketing either at weaning or at 400 d.

Abortion, Veterinary↗
PubMed1990

Effect on embryo survival of short-term exposure to the uterine environment of two selected lines of mice.

Two genetic lines of mice (Mus musculus), one selected for high embryo survival (Line E) and the other for small litter size (Line CN-), were used as models to study preimplantation embryo survival. The two lines displayed similar ovulation rates, but significantly lower embryo survival to implantation was observed in Line CN- females (P less than 0.01). The effect of the uterine environment on embryo survival was examined by incubating embryos in pseudopregnant host females for 26 hours beginning at 1500 hours on day 2 (day of copulatory plug = day 0). Embryos were then removed from the host and transferred to recipient uteri of the same genetic line as the embryos for development to term. Survival of embryos was significantly greater after exposure to Line E hosts (P less than 0.01). Survival of Line E embryos was reduced from 71% in Line E hosts to 28% in Line CN- hosts. Survival of Line CN- embryos increased from 17% in Line CN- hosts to 70% in Line E hosts. Embryos also were cultured in vitro in uterine flushings collected from each line. More Line E embryos developed to the blastocyst stage than did Line CN- embryos (P less than 0.01). Development of Line CN- (P less than 0.01) embryos, but not Line E embryos, was affected by the line from which uterine flushings were collected. These lines of mice provide a useful model for the study of the physiological basis for differences in embryo survival due to genetic selection.

Animals↗
PubMed1989

Competition between split and nonmanipulated embryos in the production of identical piglets.

The effect of nonmanipulated embryos on in utero survival of split porcine embryos was examined in this study. Previously, only limited success in the production of identical twin piglets has been reported. Embryos were collected from slaughtered donors (4 to 7 d post estrus) and were either split with the aid of a micromanipulator or left as whole embryos. Monozygotic pairs of split embryos were then surgically transferred to recipients with a complement of either split or nonmanipulated embryos. A total of 217 split embryos and 60 nonmanipulated embryos were transferred to 19 recipients. Nine of these recipients farrowed. In the two recipients that received only split embryos and farrowed, 31% of the split embryos survived to term, including two sets of monozygotic twins. In the remaining seven recipients, only 10% of the split embryos that were transferred along with nonmanipulated embryos survived to farrowing. This difference in split embryo survival (31 vs 10%) was significantly different (P<0.005). Sixty-nine percent of the nonmanipulated embryos survived to term in recipients that maintained pregnancy. Data presented in this study suggest that competition occurs between split and nonmanipulated embryos transferred to the same uterine environment.

Journal Article↗
PubMed1989

Survival of sheep x goat hybrid inner cell masses after injection into ovine embryos.

Modified blastocyst injection techniques were used to inject immunosurgically isolated sheep x goat hybrid inner cell masses (ICM) into ovine blastocysts, with subsequent transfer of composite embryos to ovine recipients. Hybrid embryos were collected from does artificially inseminated with Barbados ram semen. A total of 13 live and 2 aborted offspring resulted from the 34 composite embryos transferred to recipient ewes (38% embryo survival). Of the 15 offspring, 4 exhibited phenotypic hybridism and 2 (13%) of these were determined to be hybrid mean value of -sheep chimeras by karyotype, serum protein and isoenzyme analyses, and fiber identification. Each of the 4 was produced by an injection procedure that involved damage of the ovine host ICM. One additional offspring was unusual in appearance, but the presence of hybrid cells was not proven. Similarly, caprine ICM were immunosurgically isolated and injected into ovine blastocysts that were then transferred to ovine recipients. Of the 13 composite embryos transferred, 12 offspring were produced (92% embryo survival). Eleven were overt goat mean value of -sheep chimeras and, of these, 7 were also blood chimeras. The hybrid ICM was shown to be capable of contributing to normal embryonic and fetal development after injection into an ovine blastocyst but may be less likely to be incorporated with the ovine host ICM than is the caprine ICM.

Animals↗
PubMed1988

Viability of blastocysts produced by aggregation of two half-embryos in the mouse.

Although methods for production of chimeras from early cleavage stages have been well established, little research has been directed toward production of genetically identical chimeric offspring. This study was designed to examine survival of blastocysts produced by aggregation of two halved eight-cell stage embryos from two different mouse strains. Four blastomeres of an eight-cell embryo from a pigmented strain were aggregated with four blastomeres of an eight-cell embryo from a nonpigmented strain. Aggregates were cultured for 48 h and transferred as blastocysts to synchronized recipients of three treatment groups. Viability was determined by examining the number of offspring produced relative to the number of blastocysts transferred. Thirty-nine pups were born from 375 transferred blastocysts (10%), with 16 pups displaying coat-color chimerism. Both nonmanipulated eight-cell embryos cultured for 48 h (P < 0.05) and chimeric blastocysts (P < 0.001) displayed lower embryo survival after transfer to recipients than noncultured, nonmanipulated blastocysts used as controls. Viability of chimeric blastocysts was also lower than that of nonmanipulated embryos cultured for the same period and transferred to the same recipients (P < 0.001). Although posttransfer survival of chimeric blastocysts was low, the birth of morphologically normal offspring demonstrated that production of chimeras from half embryos was compatible with survival. Improvements in this procedure may be useful for production of tenetically identical chimeras from outbred populations, such as those commonly found in domestic livestock species.

Journal Article↗
PubMed1988

Interspecific pregnancy: barriers and prospects.

Investigations on the mechanisms that allow survival of the fetal allograft have been extended by pregnancies in which the fetus and pregnant female are from different species. Such interspecific pregnancies are useful models for the study of maternal/fetal interactions and also may assist in the preservation of endangered species. Results of experiments with three different interspecific model systems are discussed: a murine model using Mus musculus and M. caroli; an equine model involving primarily the domestic horse and donkey, but including several wild Equidae; and a bovid model that crosses genera--pregnancy between the domestic sheep and goat. Species differences are reflected in results of experiments involving the various models. An immunological barrier appears to restrict interspecific pregnancy, but how the barrier is manifested appears to differ with species. Evidence for inappropriate interaction between trophoblast and endometrium is also presented. Results of experiments aimed at overcoming barriers to interspecific reproduction are discussed.

Animals↗