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Biomedical subjects

G B Anderson

Publications and source records attributed to G B Anderson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Development of tumors from bovine primordial germ cells transplanted to athymic mice.

Intact genital ridges containing primordial germ cells (PGC) and isolated PGC from murine and bovine embryos were examined for in vivo growth and differentiation after transplantation under the kidney capsule of athymic mice. Genital ridges were collected from day 11.5 and 12.5 murine and day 34 and 37 bovine embryos. Murine genital ridges and isolated PGC collected at 11.5 days post-coitus (dpc) and isolated murine PGC collected at 12.5 dpc developed into tumors. Day 34 and 37 bovine genital ridges, but not isolated PGC developed into tumors. The bovine origin of the tumors was confirmed by an analysis of the bovine DNA sequences. Tumors from both species consisted primarily of mesoderm-derived cell types, including connective tissue, cartilage, smooth muscle, fibroblasts, osteoblasts and bone matrix. No detectable ectodermal derivatives were observed in tumors of either species. Undifferentiated stem cells were not detected in the tumors, suggesting that the tumors were benign teratomas. Results of this study demonstrate the pluripotency of bovine PGC by experimental induction of teratomas after xenotransplantation under the kidney capsule of athymic mice. Stimulation of PGC survival and proliferation in an ectopic graft could be useful toward the isolation of pluripotent embryo-derived stem cells.

Animals↗
PubMed1998

In vitro survival and proliferation of porcine primordial germ cells.

Primordial germ cells (PGC) collected from the genital ridge of Day 25 porcine embryos were cultured on STO feeder cells in medium with or without supplemented growth factors. The effects on porcine PGC proliferation of leukemia inhibitory factor (LIF), LIF + stem cell factor (SCF) or LIF + SCF + basic fibroblast growth factor (bFGF), growth factors shown to be essential for in vitro survival and proliferation of murine PGC, were tested. After histochemical staining, both freshly collected and cultured PGC expressed alkaline phosphatase activity. With or without supplemented growth factors, porcine PGC survived and proliferated in culture for at least 5 d. None of the growth factors tested markedly enhanced in vitro growth of porcine PGC. These results suggest that growth factors provided by either the STO feeder layer or the cultured PGC themselves are sufficient to support in vitro survival and proliferation of porcine PGC. With the support of STO cells, addition of growth factors shown to be essential for the in vitro growth of murine PGC is not required for survival and proliferation of cultured porcine PGC.

Animals↗
PubMed1998

Antimicrobial properties of human lysozyme transgenic mouse milk.

The antimicrobial properties of standard human lysozyme and the milk of transgenic mice expressing human lysozyme were investigated using bacterial strains important to the dairy industry. Standard human lysozyme was found to be effective at significantly slowing the growth of the milk cold-spoilage organism Pseudomonas fragi (P < 0.001), of a clinical isolate of the mastitis-causing organism Staphylococcus aureus (P < 0.005), and a nonpathogenic strain of E. coli (P < 0.05). Milk from transgenic mice secreting human lysozyme in their milk at an average concentration of 0.3 mg/ml was found to be bacteriostatic against the cold-spoilage organisms Pseudomonas fragi and Lactobacillus viscous and a mastitis-causing strain of Staphylococcus aureus, but not against a pathogenic strain of E. coli. These results demonstrate that transgenic animals producing human lysozyme in their milk can affect the microbial nature of milk.

Animals↗
PubMed1997

Production of free estrogens and estrogen conjugates by the preimplantation equine embryo.

In vitro production of free estrogens and estrogen conjugates by intact Day 12.5, 13.5 and 14.5 equine embryos was measured at 2-h intervals over a 24-h culture period. Production of free estrogens was higher for Day 14.5 than Day 12.5 embryos. Differences in production of conjugated estrogens were not significant, but a trend toward increased production with increased age of embryo was apparent. No trend toward increased free and conjugated estrogen production per cell was observed with age. Embryo diameter and number of cells increased with age but varied considerably within groups. The amount of free and conjugated estrogens measured in blastocoelic fluid did not decrease over the 24-h culture period, suggesting that estrogens detected in culture medium were produced by the embryo and not the result of leakage of maternal estrogen from the blastocoele. The results of this study support previous results that estrogen production increases with development of equine embryos. This increase in estrogen production appears to be more closely associated with the diameter of the embryo, and hence its number of cells, than with increased intracellular steroidogenic activity.

Journal Article↗
PubMed1997

Transition from maternal to embryonic control of development in IVM/IVF domestic cat embryos.

The timing of the transition from maternal to zygotic control of development (MZT) and the initiation of transcription was studied in domestic cat embryos to determine if there is a temporal association between these phenomena and the development block observed in cat embryos fertilized in vitro. Embryos were derived from in vitro-matured, in vitro-fertilized (IVM/IVF) oocytes. In Experiment 1, embryos (n = 52) were cultured continuously in the presence of 10 micrograms/ml alpha-amanitin (a transcriptional inhibitor) from 12-hr postinsemination (hpi), and cleavage stage was evaluated every 24 hr. The proportion of embryos cleaving to at least the 5-8 cell stage in the presence of alpha-amanitin (32/52) was similar (P > 0.05) to that of controls cultured without alpha-amanitin (25/50). In contrast, only 7.7% of alpha-amanitin-treated embryos cleaved to the 9-16-cell stage, compared with 38.0% of the controls (P < 0.05), indicating that products of embryonic transcription were required for cleavage beyond the 5-8-cell stage. In Experiment 2, embryos were cultured in the presence of 20 microM 3H-uridine for 12 hr beginning at 24, 36, 48, or 60 hpi and subjected to autoradiography. Embryos of 5-8-cell and 9-16-cell stages (14 of 27 and 8 of 12, respectively) clearly demonstrated nuclear labeling, a finding also confirmed by computer-aided densitometry. It is concluded that embryonic transcription and the MZT occur by the 5-8-cell stage of IVM/IVF domestic cat embryo development and the MZT is not directly related to the partial morula-to-blastocyst developmental block observed in cultured IVF cat embryos.

Amanitins↗
PubMed1997

Early transcription of the SRY gene by bovine preimplantation embryos.

We have examined mRNA expression of two genes located on the Y chromosome, the sex-determining region Y gene (SRY) and the linked zinc finger gene (ZFY), using in vitro fertilized-in vitro cultured bovine embryos. Expression of the SRY gene, implicated in sex determination in mammals, has been reported to occur both for a short time at the sex-determining stage of development around the period of the primitive undifferentiated gonad and in the adult testis. In this study, using a sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay, we detected SRY but not ZFY mRNA expression as early as the 4- to 8-cell stage and through to the blastocyst stage in bovine embryos. The expression of SRY at these early stages and the previous observation that in vitro-produced male bovine embryos develop faster in culture than female embryos suggest that sex differences are evident prior to gonadal differentiation and that preimplantation bovine embryos have sexually dimorphic gene expression at least with respect to SRY transcripts.

Animals↗
PubMed1997

Clinical effects of chlorhexidine mouthwashes on patients undergoing orthodontic treatment.

This study compared the short-term clinical effect of 0.12% chlorhexidine gluconate and placebo mouthrinses in 30 adolescents (ages 11 to 15) undergoing orthodontic treatment. Subjects were randomized into experimental (CHX) and control (C) groups. Baseline values were recorded 10 days after prophylaxis and included Plaque index (PI), Gingival index (GI), Rentention Index (RI), Discoloration index (DI), and probing depths (PD). Both groups (CHX and C) received soft toothbrushes with instructions to brush twice daily, as well as the CHX and placebo mouthrinses, respectively, with oral and written instructions for rinsing twice daily with 15 ml for 30 seconds. Reevaluations were performed 1, 2, and 3 months after baseline, except for the DI and PD, which were only assessed at 3 months. The Student's t test and the paired t test were used to analyze the data at the P < 0.05 level of significance. No differences between groups were seen at baseline for any of the parameters. At 30 days, there was a significant difference for the RI between CHX (0.15 +/- 0.16; mean +/- SD) and C (0.05 +/- 0.06) at the mesial buccal, and for CHX (0.07 +/- 0.10) and C (0.02 +/- 0.05) at the midbuccal. The 60-day evaluation showed similar results. At 90 days, lower PI were observed in the CHX group at the distal buccal (0.38 +/- 0.19), midbuccal (0.22 +/- 0.17), and mesial buccal (0.47 +/- 0.22) sites as compared with the C group (0.97 +/- 0.38, 0.83 +/- 0.40, and 0.95 +/- 0.43, respectively). A similar trend was noted with the GI, as the lower values were related to the CHX group. The changes of the PI and GI, at 30, 60, and 90 days, as analyzed by the paired t test, were statistically significant in the case of the experimental group, as the changes in the means were a reflection of significantly lower scores observed in the experimental group. After 3 months, the DI showed higher scores in the experimental group as compared with the control, but they were not statistically significant. Deeper PD were detected in the C group at 90 days, and they were statistically significant, except for the midlingual site. The RI did not show significant differences at 90 days, but higher values were recorded in the CHX group. The data indicate that the use of the CHX, in addition to regular oral hygiene habits, was effective in reducing plaque and gingivitis in adolescents undergoing orthodontic treatment.

Adolescent↗
PubMed1997

Isolation of pluripotent stem cells from cultured porcine primordial germ cells.

Embryonic germ (EG) cells are undifferentiated stem cells isolated from cultured primordial germ cells (PGC). To date, EG cells have been isolated only in the mouse. Murine EG cells share several characteristics with embryonic stem (ES) cells, including morphology, pluripotency, and the capacity for germline transmission. We report here the isolation of porcine EG cells. PGC collected from Day 24 or 25 porcine embryos were cultured on mitotically inactivated murine fibroblasts. Four EG cell lines were isolated from repeated subculture of porcine PGC. Porcine EG cells morphologically resembled murine ES cells and consistently expressed alkaline phosphatase activity. These cell lines maintained a normal diploid karyotype and survived after cryopreservation. Porcine EG cells were capable of differentiating into a wide range of cell types in culture, including endodermal, trophoblast-like, epithelial-like, fibroblast-like, and neuron-like cells. In suspension culture, porcine EG cells formed embryoid bodies. When injected into host blastocysts, the EG cells were able to differentiate and contribute to tissues of a chimeric piglet. Both in vitro and in vivo evidence demonstrates that the isolated EG cells were pluripotent. These cells are potentially useful for genetic manipulation in pigs.

Alkaline Phosphatase↗
PubMed1997

Experience with computed tomographic angiography for the detection of intracranial aneurysms in the setting of acute subarachnoid hemorrhage.

OBJECTIVE: To objectively compare computed tomographic angiography (CTA) with selective digital subtraction angiography (DSA) in the detection and anatomic definition of intracranial aneurysms, particularly in the setting of acute subarachnoid hemorrhage (SAH). METHODS: In a blinded prospective study, 40 patients with known or suspected intracranial saccular aneurysms underwent both CTA and DSA, including 32 consecutive patients with SAH in whom CTA was performed after CT images were obtained diagnostic for SAH. The CT angiograms were interpreted for presence, location, and size of the aneurysms, and anatomic features, such as the number of aneurysms lobes, aneurysm neck size (< or = 4 mm), and the number of adjacent arterial branches were suggested. The images obtained with CTA were then compared with the images obtained with DSA, with the later images serving as controls. RESULTS: DSA revealed 43 aneurysms in 30 patients and ruled out intracranial aneurysms in the remaining 10 patients. For aneurysm presence alone, the sensitivity and specificity for CTA was 86 and 90%, respectively. For the presence of an aneurysms, six CT angiogram showed false negative results and one CT angiogram showed a false positive result. False negative results were usually caused by technical problems with the image, tiny aneurysm domes (< 3 mm), and unusual aneurysm locations (i.e., intracavernous carotid or posterior inferior cerebellar artery aneurysms). The results obtained with CTA were, compared with the results obtained with DSA, more than 95% accurate in determining dome and neck size of aneurysm, aneurysm lobularity, and the presence and number of adjacent arterial branches. In addition, CTA provided a three-dimensional representation of the aneurysmal lesion, which was considered useful for surgical planning. CONCLUSION: CTA is useful for rapid and relatively noninvasive detection of aneurysms in common locations, and the anatomic information provided in images showing positive results is at least equivalent to that provided by DSA. In cases of SAH in which the nonaugmented CT and CTA results indicate a clear source of bleeding and provide adequate anatomic detail, we think it is possible to forego DSA before urgent early aneurysm surgery. In all other cases, DSA is indicated.

Acute Disease↗
PubMed1997

Ovine-specific Y-chromosome RAPD-SCAR marker for embryo sexing.

An accurate, sensitive, and quick (approximately 3 h) method for determining the sex of ovine embryos was developed using polymerase chain reaction (PCR) primers derived from an ovine-specific Y-chromosome random amplified polymorphic DNA marker (UcdO43). The accuracy and sensitivity of the assay were first tested using genomic DNA from 10 males and 10 females of five different sheep breeds, and then tested using serial dilutions of male-in-female DNA. The assay was 100% accurate in confirming the sex of the individuals and the ovine male-specific fragment was detected in dilutions containing as little as 10 pg of male DNA in 50 ng of female DNA. The assay was also confirmed to be specific for the ovine Y-chromosome as bovine, caprine, porcine, murine, and human DNA did not amplify. The ovine embryo sexing method is a duplex PCR system that also includes ZFY/ZFX primers. ZFY/ZFX provide an internal positive control for amplification as well as a means to confirm the results obtained with the UcdO43 primers. All embryo sexing results (36/36) from our method were in agreement with the ZFY/ZFX assay results. However, while our method requires an internal control to detect PCR failure, it has the advantages of not requiring nested PCR or restriction endonuclease digestion of the PCR product, and concerns about cross-species contamination are eliminated.

Animals↗
PubMed1997

Healing of intrabony defects and its relationship to root canal therapy. A histologic and histometric study in dogs.

The purpose of this study was to evaluate the importance of root canal therapy in the healing process of severe intrabony defects. Four beagle dogs were used and 32 interproximal intrabony defects, up to the apical third, were created. Wire ligatures were placed into these defects for plaque accumulation. Three weeks later, the ligatures were removed and 4 different treatment modalities were employed: group 1) scaling and root planing (SRP); group 2) modified Widman flap (MWF); group 3) modified Widman flap and root canal therapy performed at the same time (RCT/MWF); and group 4) modified Widman flap and root canal therapy performed 3 weeks after the surgical procedure (MWF + RCT). Postoperative oral hygiene was obtained by spraying a 0.12% chlorhexidine solution 3 times a week. The animals were sacrificed 7 weeks after treatment. Blocks were obtained and processed for routine histology. Results were expressed as a percentage of the total defect length (TDL). No differences were observed when SRP was compared to MWF. New bone formation (BF) presented better results for SRP (43.4%) and MWF (53.4%) when compared to RCT/MWF (15.5%). New cementum formation (CF) presented better results for SRP (59.8%) and MWF (64.6%) when compared to RCT/MWF (19.3%) and MWF + RCT (31.5%). Connective tissue repair (CTR) presented better results for SRP (72.4%) and MWF (74.2%) when compared to RCT/MWF (47.5%) and MWF + RCT (44.4%). Results were statistically significant at the level of 0.05. Within the limits of this study, it was concluded that root canal therapy performed simultaneously or 3 weeks after surgery modified the healing of intrabony defects, impairing new bone formation, new cementum formation and new attachment.

Alveolar Bone Loss↗
PubMed1996

Development of bovine and porcine embryonic teratomas in athymic mice.

Inner cell masses (ICM) and embryonic discs from bovine and porcine blastocysts of various ages were transplanted under the kidney capsule of athymic (nude) mice to evaluate growth of teratocarcinomas containing both differentiated tissues and undifferentiated stem cells. Inner cell masses were isolated immunosurgically from Day 8, Day 9 and Day 10 porcine blastocysts and from Day 8, Day 10 and Day 12 bovine blastocysts. Embryonic discs were mechanically dissected from Day 11 and Day 12 porcine embryos and from Day 14 bovine embryos. Day 6 egg cylinders were dissected from BALB/C embryos and from hybrid embryos of a cross between BALB/C and an outbred strain of mouse. Two to four ICM, embryonic discs or egg cylinders were transplanted under the kidney capsule of each athymic host. After 8 weeks, graft hosts were killed and their tumors removed, fixed and prepared for histological and immunohistochemical examination. Embryonic teratomas developed at high frequency from murine egg cylinders and from Day 11 and Day 12 porcine and Day 14 bovine embryos. Tumors were observed only infrequently from younger bovine and porcine blastocysts. Murine embryonic tumors were composed of numerous differentiated cell types of ectodermal, mesodermal and endodermal origins, but representation of the three embryonic germ layers was somewhat more restricted in bovine and porcine embryonic tumors. No undifferentiated stem cells were detected in tumors of any of the three species. These results demonstrate that teratomas will develop from bovine and porcine embryos when grafted to an immunocompromised host, but the presence of undifferentiated teratocarcinoma stem cells from these species has yet to be achieved.

Animals↗
PubMed1996

Phase transition temperature and chilling sensitivity of bovine oocytes.

A limiting factor for achieving cryopreservation of oocytes is direct chilling injury (DCI), which occurs during cooling. DCI, or cold shock, is defined as an irreversible damage expressed shortly after exposure to low, but not freezing, temperatures. The primary target of DCI is thought to be the plasma membrane. Recently, an association between DCI in sperm and the thermotropic phase transition of their membrane lipids was demonstrated. In the present study, we examined the phase transition of the membrane lipids of immature and in vitro-matured bovine oocytes during cooling, using Fourier transform infrared spectroscopy (FTIR). The phase transition of the membrane lipids of oocytes at the germinal vesicle (GV) stage occurred between 13 and 20 degrees C, while a very broad phase transition, which centered around 10 degrees C, was observed for mature oocytes (MII) stage. Thermotropic phase transitions were demonstrated to be related to the temperature at which DCI affected the integrity of the oocyte membranes. When immature oocytes were cooled to 13 degrees C, fewer oocytes (40%) retained their membrane integrity than after exposure to 4 degrees C (51%) or holding them at 38 degrees C (78%), (as determined by the Fluorescein Diacetate-FDA test). This finding might suggest that holding immature oocytes at the phase transition temperature is more damaging to their membranes than exposure to lower temperatures. By contrast, no significant differences in membrane integrity were observed when in vitro-matured oocytes were cooled to the same temperatures. Subsequently, GV oocytes were cooled to 4 degrees C, and 26% underwent maturation and 19% underwent fertilization in vitro. In vitromatured oocytes that were cooled to 4 degrees C displayed a slightly decreased rate of fertilization; the overall fertilization was 60% with 24% polyspermy, rather than the 76% fertilization rate with 12% polyspermy obtained with those not subjected to cooling. The high rate of polyspermy indicates that a site(s) other than the plasma membrane is affected during cooling of bovine oocytes. Nucleated bovine GV oocytes were electrofused with in vitro-matured and enucleated oocytes, and then cooled to 4 degrees C. Evaluation of the membrane integrity of the fused oocytes showed that these oocytes are chilling resistant, which strongly suggests that alteration of the membrane composition of an oocyte can change the cell's susceptibility to low temperatures. This finding led to an improvement in the survival of oocytes after cryopreservation.

Animals↗
PubMed1996

Expression of a bovine kappa-CN cDNA in the mammary gland of transgenic mice utilizing a genomic milk protein gene as an expression cassette.

Transgenic mice were produced by microinjection of a DNA construct composed of the bovine kappa-casein (kappa-CN) cDNA under the control of the goat beta-CN 5' promoter elements and 3' flanking regions into pronuclear-stage embryos. The gene construct targeted the expression of bovine kappa-CN RNA to the mammary gland and secretion of bovine kappa-CN in the milk. In the three lines studied (BC-7, BC-31 and BC-67) the transgene was stably integrated and propagated as a Mendelian locus. Expression of the bovine protein in lactating mice from the three transgenic lines was demonstrated by northern and western blots. In ten different tissues analysed by northern blotting, expression was confined to the mammary gland of lactating transgenic mice from line BC-7, with low-level expression also observed in the salivary gland of lines BC-31 and BC-67. Transgene expression in the mammary gland paralleled normal casein gene expression during lactation and was not observed in virgin females. The level of bovine kappa-CN mRNA expression on day 10 of lactation in hemizygous transgenic females in relation to endogenous mRNA of whey acid protein (WAP) gene expression was 14%, 69%, and 127% in lines BC-7, BC-31 and BC-67, respectively. No association between transgene copy number and expression was observed. The bovine kappa-CN concentration in milk on day 10 of lactation ranged from 0.94 to 3.85 mg of protein per ml of milk. The bovine kappa-CN expressed in mouse milk had the same molecular mass and immunoactivity with polyclonal antibodies as did kappa-CN from bovine milk. A high degree of variation in the production of bovine kappa-CN within each of the transgenic lines was observed.

Amino Acid Sequence↗
PubMed1996

Effectiveness of subgingival scaling and root planing: single versus multiple episodes of instrumentation.

This study evaluates the effectiveness of subgingival scaling and root planing comparing the effect of a single instrumentation to the effect of three instrumentations. A total of 35 teeth in 15 patients were selected; 15 were scaled once (Group A), 15 were scaled three times (Group B), and 5 were used as controls (Group C), representing teeth that were not instrumented. The Group A and B teeth were chosen in the same patient based on random selection. All the teeth were scored by the calculus index of the periodontal disease index. Six surface locations were probed to determine probing depth. The level of the gingival margin was marked on the teeth to locate supra- and subgingival calculus after extraction. The Group A and B teeth received the initial episode of scaling and root planing for not more than 10 minutes, then only the Group B teeth received two additional instrumentations of not more than 5 minutes each. The additional instrumentations were performed 24 hours after the initial scaling. The scaled and control teeth were extracted immediately after the third instrumentation period. The teeth were washed with water and stained with methylene blue. They were viewed under a stereomicroscope which had a tenth grid on its eyepiece. Assessments were made involving the total counts and percents of the surfaces covered with calculus on the scaled and unscaled teeth. The results demonstrated no significant difference in the effectiveness of calculus removal between single and multiple episodes of scaling and root planing. Similar results were found for the total amount of calculus removed, the calculus removed from individual surfaces, and the calculus removed from various probing depth levels.

Adult↗
PubMed1996

Alterations of the physical characteristics of milk from transgenic mice producing bovine kappa-casein.

kappa-Casein is the protein fraction of milk that allows formation of micelles and determines micelle size and function, thus affecting many of the physical characteristics of milk. Several lines of transgenic mice were generated bearing the B allele of the bovine kappa-CN gene under the control of the regulatory sequences of the caprine beta-CN gene that specifically directed expression of bovine kappa-CN to the lactating mammary tissue of these mice. High expression of bovine kappa-CN protein was observed in the lines studied; the total level of protein in milk was not significantly affected. A high degree of conservation in the amino acids involved in the predicted three-dimensional structure exists between murine and bovine kappa-CN. Milk from transgenic lines expressing high bovine kappa-CN had a significantly smaller micelle size than did control milk. Therefore, bovine kappa-CN appears to have effectively participated in assembly of murine casein micelles. There was no effect on the time of rennet coagulation, but the association was significant between the milk of transgenic lines and the production of a stronger curd in rennet-induced gels. We conclude that bovine kappa-CN is an appropriate candidate for transgenic technology that would increase the ratio of kappa-CN to the calcium-sensitive caseins, therefore affecting the physical properties of the colloidal casein suspension.

Amino Acid Sequence↗