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Biomedical subjects

D L Davis

Publications and source records attributed to D L Davis.

At least 19 recordsLinked to original sources
PubMed2004

Fertilization and blastocyst development in oocytes obtained from prepubertal and adult pigs.

Polyspermic fertilization and embryo quality are important issues for the in vitro production of pig embryos. We hypothesized that oocyte donor (prepubertal gilt vs. sow) affects polyspermy and blastocyst development in vitro and that the sexual maturity of the oocyte donor affects the response to sperm concentration in the fertilization medium. In Exp. 1, oocytes of sows and gilts were mounted and stained 12 h after insemination to provide fertilization data. In Exp. 2, putative embryos were developed in vitro to 144 h post-insemination before mounting. In both experiments, cumulus-oocyte complexes (COC) were collected from ovaries of prepubertal gilts and adult sows. Sperm were added after maturation of COC for 40 to 44 h. Sperm from two boars at 0.5 to 5.0 x 10(6) sperm/mL was used for insemination. More (P < 0.01) monospermic fertilizations were observed in oocytes derived from gilts than for oocytes from sows. There were fewer (P < 0.02) penetrated sperm per fertilized oocyte in oocytes from gilts compared with sows. There were effects of semen donor (boar) on the percentage of monospermic (P < 0.01) and polyspermic (P < 0.002) fertilizations, and on the number of penetrated sperm/fertilized oocyte (P < 0.02). In Exp. 2, cleavage and blastocyst formation was evaluated at 2 and 6 d postinsemination, respectively. More (P < 0.001) blastocysts developed from sow-derived oocytes than from gilt-derived oocytes. More (P < 0.05) total cells per blastocyst were observed in embryos from sow-derived oocytes than from gilt-derived oocytes. Semen donor affected the percentage of oocytes cleaving (P < 0.02), and a boar x sperm concentration interaction affected (P < 0.05) the incidence of blastocyt formation. Results indicate that sexual maturity of the donor is not responsible for the high incidence of polyspermy in porcine in vitro fertilization. However, blastocyst development is improved by the use of oocytes from sows rather than from prepubertal gilts.

Animals↗
PubMed2004

Conceptus and maternal responses to increased feed intake during early gestation in pigs.

Maternal diet influences fetal growth and postnatal development. We hypothesized that conceptuses gestated in sows provided ad libitum vs. restricted feed intake would differ in the milieu of hormones, growth factors, nutrients, and metabolites associated with growth and metabolism. This hypothesis was tested in two experiments by providing fourth-parity sows (Pig Improvement Co. C15 bred to Line 326 boars) with either 1.81 kg/d (as-fed basis; control) or ad libitum access to gestation diet. In Exp. 1, control (n = 6) or ad libitum (6.4 +/- 0.11 kg/d; n = 9) treatments were provided from d 29 to 45 (onset of estrus is d 0), and sows were slaughtered on d 46. Ad libitum sows gained more weight from d 29 to 45 than controls (34.0 vs. 4.32 kg, respectively; P < 0.01). No differences were observed on d 46 for the number of fetuses, conceptus attachment length, allantoic + amniotic fluid volume, placental weight, fetal weight, and fetal crown-to-rump length. Variation in fetal crown-to-rump length was less (P < 0.03) in sows fed ad libitum. Sows fed ad libitum had greater (P < 0.01) IGF-I and insulin concentrations in plasma than controls on d 43. In Exp. 2, sows were fed 1.81 kg/d (n = 6) or ad libitum (7.0 +/- 0.11 kg/d; n = 4) from d 30 to 56 of gestation, when sows were anesthetized and samples were collected surgically from their gravid uteri. Sows fed ad libitum gained more weight (P < 0.01) than did controls and had more (P < 0.06) IGF-I in their plasma and the plasma collected from umbilical veins of their fetuses. No differences were found for concentrations of insulin or glucose in plasma of sows or fetuses, but urea N concentrations were greater (P < 0.05) in maternal plasma and in the plasma, and allantoic and amniotic fluids of conceptuses from sows fed ad libitum. Combined data from Exp. 1 and 2 revealed a treatment x fetal number interaction (P < 0.05) for average fetal weight. The expected negative relationship between within-litter average fetal weight and the number of fetuses per uterus was observed for control sows (y = 115.4 -1.75 x fetal number; P < 0.05), but litters of ad libitum sows did not show this effect. The hypothesis that providing feed in excess of established requirements in early gestation affects the in utero milieu is supported by these results. Data further reveal that, at least at mid-gestation, the restraint to fetal growth that is exhibited when fetal number increases in control sows is not exhibited when sows are fed ad libitum.

Animal Feed↗
PubMed2003

Incorporation of bovine bone marrow stromal cells into porcine foetal tissues after xenotransplantation.

Bovine bone marrow stromal cells (BMSCs) were injected into the liver of foetal pigs at about 40 days of gestation to test whether these cells could populate developing tissue, and if so, which ones. Approximately 40 days after injection, the foetuses were harvested and tissue sections from many areas of the body were analysed for the presence of bovine cells using two different methods. First, using PCR, bovine repetitive DNA was found to be present in DNA extracted from foetal pig tissues. Secondly, using oligonucleotide primed in situ synthesis (PRINS), the in situ presence of bovine cells was found within porcine tissue sections. PRINS-labelled cells were found within cartilage, perichondrium, connective tissue and smooth muscle. These data suggest that bovine BMSCs integrate throughout the foetal pig.

Animals↗
PubMed2003

Evaluation of the uterine environment and embryos of prepubertal gilts.

A series of three experiments was conducted to test the functional status of the uterus and embryos in prepubertal gilts. In Exp. 1, gilts were induced to ovulate by treating with gonadotropins followed by hCG 72 or 96 h later, and were artificially inseminated 24 h after hCG. Five of the 10 gilts treated at 120 d of age, but none of the gilts treated at 100 of age, maintained pregnancies. We next tested the function of the uterine environment by transferring embryos from postpubertal females into gilts of various ages that had been induced to ovulate but not inseminated (Exp. 2). Pregnancy rate at d 50 of gestation was 44% (4/9) for 100-d-old recipients, 67% (2/3) for 140-d-old recipients, and 60% (3/5) for postpubertal recipients (P > 0.20). Therefore, uteri of 100-d-old gilts are able to maintain pregnancies with conceptuses from postpubertal gilts. In Exp. 3, embryos from 100-d-old and postpubertal gilts were transferred into postpubertal recipients. Uterine horns of recipients were surgically separated before transfer, and embryos from 100-d-old and post-pubertal females were transferred to opposite horns of some recipients (experimental). Other recipients received embryos from postpubertal females in both uterine horns (control). When examined on d 50 to 60 of gestation, three of five control gilts were pregnant and three of seven experimental gilts were pregnant (P > 0.50). In experimental recipients, the survival of embryos from 100-d-old gilts was 38% (8/21) compared to 57% (15/26) for embryos from postpubertal gilts (P > 0.30). Because all uterine horns of pregnant recipients contained fetuses, these results support the hypothesis that embryos from 100-d-old gilts are able to initiate and maintain pregnancies in the uteri of postpubertal gilts. Therefore, the uterine environment of 100-d-old gilts provides an environment that supports development of embryos produced by postpubertal gilts, and the embryos produced by 100-d-old gilts can survive and develop in the uteri of postpubertal gilts. It was only the combination of embryos and uteri of 100-d-old gilts that did not permit pregnancy to be maintained.

Age Factors↗
PubMed2002

Retinol and estradiol regulation of retinol binding protein and prostaglandin production by porcine uterine epithelial cells in vitro.

Secretion into the uterine lumen follows a precise pattern during early pregnancy. Near the end of the second week of pregnancy and coincident with elongation of conceptuses, retinol, retinol binding protein (RBP), estradiol (E2), and prostaglandins E (PGE) and F (PGF) increase in the uterine lumen, and RBP mRNA increases in the endometrium. In the present studies the potential for E2 (0.1 microM) and retinol (10 microM) to regulate RBP and PG production by cultured luminal (LEC) and glandular (GEC) epithelial cells collected from postpubertal females and LEC from prepubertal gilts was examined. Endometrial tissue was collected surgically from cyclic and pregnant females (n = 8) on d 10 and 13 postestrus (first day of estrus = d 0) and from 120- and 150-d-old prepubertal gilts that were treated with progesterone (P4) (2.2 mg x kg(-1) x d(-1), n = 6) or corn oil (n = 6) for 14 d prior to tissue collection. The LEC from postpubertal females responded to retinol with increased (P < 0.05) RBP, PGE, and PGF in culture medium and increased (P < 0.07) RBP mRNA but E2 decreased (P < 0.05) RBP and RBP mRNA and had no effect on prostaglandins. No E2 or retinol effects on secretions of GEC occurred in vitro, but a day x pregnancy status interaction (P < 0.06) affected PGE output by the GEC. Secretion of PGE was greater when GEC were collected on d 10 of pregnancy than from d-10 cyclic or d-13 pregnant or cyclic females. Both E2 and retinol stimulated (P < 0.05) secretion of RBP by LEC isolated from prepubertal gilts, but their effects were not additive. In vivo treatment of prepubertal gilts with P4 increased (P < 0.05) RBP and decreased (P < 0.05) PG production by LEC in vitro. Therefore responses to E2 and retinol differ between pre- and post-pubertal females, and retinol may function in the regulation of endometrial RBP and PG secretion.

Animals↗
PubMed2001

Boundary conditions on the partitioning of deaminatively generated benzyl cations.

Nitrogenous entity-separated ion pairs (NESIPs) containing benzyl cations, nitrogen gas, and pivalate anions were generated via thermal deamination of N-benzyl-N-nitrosopivalamide. Some decompositions were performed in methanolic solutions saturated with selected nucleophiles: acetate, azide, or cyanide ions. Trace amounts of benzyl cyanide and tolunitriles were observed; no corresponding products were detected in the acetate and azide cases. Other decompositions were performed in the absence of traditional solvent but in the presence of the nucleophilic salts; again only poor cyanide interception of the cation was observed. The poor showing of the nucleophilic ions, when present, is discussed in the context of the lifetime of the cation, effective nucleophilicity, and cage effects in deamination.

Journal Article↗
PubMed2001

A GATA-6 gene heart-region-specific enhancer provides a novel means to mark and probe a discrete component of the mouse cardiac conduction system.

The transcriptional programs that specify the distinct components of the cardiac conduction system are poorly understood, in part due to a paucity of definitive molecular markers. In the present study we show that a cGATA-6 gene enhancer can be used to selectively express transgenes in the atrioventricular (AV) conduction system as it becomes manifest in the developing multichambered mouse heart. Furthermore, our analysis of staged cGATA-6/lacZ embryos revealed that the activity of this heart-region-specific enhancer can be traced back essentially to the outset of the cardiogenic program. We provide evidence that this enhancer reads medial/lateral and anterior/posterior positional information before the heart tube forms and we show that the activity of this enhancer becomes restricted at the heart looping stage to AV myocardial cells that induce endocardial cushion formation. We infer that a deeply-rooted heart-region-specific transcriptional program serves to coordinate AV valve placement and AV conduction system formation. Lastly, we show that cGATA-6/Cre mice can be used to delete floxed genes in the respective subsets of specialized heart cells.

Animals↗
PubMed2001

Reassessment of the lethal London fog of 1952: novel indicators of acute and chronic consequences of acute exposure to air pollution.

This article develops and assesses novel indicators of respiratory and other morbidity and mortality following London's lethal smog in the winter of 1952. Public health insurance claims, hospital admission rates for cardiac and respiratory disease, pneumonia cases, mortality records, influenza reports, temperature, and air pollutant concentrations are analyzed for December-February 1952-1953 and compared with those for the previous year or years. Mortality rates for the smog episode from December 1952 to February 1953 were 50-300% higher than the previous year. Claims that the smog only elevated health risks during and immediately following the peak fog 5-9 December 1952 and that an influenza epidemic accounted fully for persisting mortality increases in the first 2 months of 1953 are rejected. We estimate about 12,000 excess deaths occurred from December 1952 through February 1953 because of acute and persisting effects of the 1952 London smog. Pollution levels during the London smog were 5-19 times above current regulatory standards and guidelines and approximate current levels in some rapidly developing regions. Ambient pollution in many regions poses serious risks to public health.

Acute Disease↗
PubMed2001

Assessing the health benefits of urban air pollution reductions associated with climate change mitigation (2000-2020): Santiago, São Paulo, México City, and New York City.

To investigate the potential local health benefits of adopting greenhouse gas (GHG) mitigation policies, we develop scenarios of GHG mitigation for México City, México; Santiago, Chile; São Paulo, Brazil; and New York, New York, USA using air pollution health impact factors appropriate to each city. We estimate that the adoption of readily available technologies to lessen fossil fuel emissions over the next two decades in these four cities alone will reduce particulate matter and ozone and avoid approximately 64,000 (95% confidence interval [CI] 18,000-116,000) premature deaths (including infant deaths), 65,000 (95% CI 22,000-108,000) chronic bronchitis cases, and 46 million (95% CI 35-58 million) person-days of work loss or other restricted activity. These findings illustrate that GHG mitigation can provide considerable local air pollution-related public health benefits to countries that choose to abate GHG emissions by reducing fossil fuel combustion.

Adolescent↗
PubMed2001

Development of porcine embryos in vitro: effects of culture medium and donor age.

We compared development of porcine embryos in three media and evaluated the effect of age of the donor on embryo development in vitro. In Exp. 1, embryos were collected from 35 postpubertal females on d 2 or 3 after onset of estrus. Embryos were cultured 144 h in Whitten's Medium (WM), North Carolina State University Medium-23 (NCSU-23), or Beltsville Embryo Culture Medium-3 (BECM-3) in 95% air: 5% CO2 at 39 degrees C. More (P < 0.01) embryos that were initially one cell or two cells developed to blastocysts when cultured in NCSU-23 (56%) and BECM-3 (43%) rather than in WM (7.5%). More (P < 0.01) embryos that were four cells at recovery developed to blastocysts in NCSU-23 (97%) than in BECM-3 (69%) or WM (69%). Blastocysts that developed from four-cell embryos cultured in BECM-3 had more (P < 0.01) nuclei than blastocysts that developed from four-cell embryos in the other two media. In Exp. 2, ovarian responses, fertilization rates, and in vitro embryo development in NCSU-23 and BECM-3 were compared for postpubertal (approximately 170-d-old) gilts vs gilts given exogenous gonadotropins at 102 d of age. Ovulation rate (P < 0.01), number of eggs recovered, and number of eggs fertilized per gilt (P < 0.001) were greater in the older gilts. The percentage of eggs fertilized, the number of unfertilized eggs, and the number of unclassifiable eggs were similar (P > 0.10) for both age groups. More (P < 0.10) blastocysts developed from embryos recovered from 170-d-old than from 102-d-old gilts, and more (P < 0.05) blastocysts developed in NCSU-23 than in BECM-3. Zona thicknesses and number of nuclei per embryo were similar (P > 0.10) for both ages. We conclude that embryos from prepubertal gilts do not have the same in vitro developmental potential as those from cyclic gilts. However, superior development of embryos in NCSU-23 from both 102-d-old and 170-d-old gilts indicates that media composition did not differentially affect embryos produced by younger vs older gilts.

Age Factors↗
PubMed2001

Genetic analysis of intestinal cholesterol absorption in inbred mice.

A genetic mapping strategy was employed to identify chromosomal regions harboring genes that influence the absorption of intestinal cholesterol in the mouse. Analysis of seven inbred strains of male mice (129P3, AKR, BALB/c, C3H/He, C57BL/6, DBA/2, and SJL, all from Jackson Laboratories) revealed substantial differences in their abilities to absorb a bolus of cholesterol delivered by gavage. Crosses between high (AKR, 129) and low (DBA/2, SJL) absorbing strains revealed evidence for the presence of dominant genes that increase and decrease cholesterol absorption. Backcrosses between F1 offspring and parental strains (DBA/2xAKD2F1 and 129xSJL129F1) followed by linkage analyses revealed four quantitative trait loci that influenced cholesterol absorption. Analyses of recombinant inbred strains identified an additional three loci affecting this phenotype. These seven quantitative trait loci, which map to different chromosomes and are termed Cholesterol absorption 1-7 (Chab1-7) loci, together influence the absorption of intestinal cholesterol in mice and are likely to be involved in different steps of this complex pathway.

Animals↗
PubMed2001

Genetic analysis of cholesterol accumulation in inbred mice.

Genetic linkage analysis in the laboratory mouse identified chromosomal regions containing genes that contribute to cholesterol accumulation in the liver and plasma. Comparisons between five inbred strains of mice obtained from the Jackson Laboratory (DBA/2, AKR, C57BL/6, SJL, and 129P3) revealed a direct correlation between intestinal cholesterol absorption and susceptibility to diet-induced hypercholesterolemia. This correlation was lost in the F1 generation arising from crosses between high- and low-absorbing strains. Linkage analyses in AKxD recombinant inbred strains and 129xSJL129F1 N2 backcross mice identified four quantitative trait loci (QTL) that influenced Liver cholesterol accumulation (Lcho1-4) and one locus that affected Plasma cholesterol accumulation (Pcho1). These loci map to five chromosomes and, with one exception, are different from the seven QTL identified previously that influence intestinal cholesterol absorption. We conclude that a large number of genes affects the amount of cholesterol absorbed in the small intestine and its accumulation in the liver and plasma of inbred mice.

Animals↗
PubMed2000

Identification of ubiquitin as an immunophilin.

We have identified an 8.4 kDa minor immunophilin from calf thymus and Jurkat T cells as ubiquitin. It binds tacrolimus and sirolimus with K(d)'s of 0.8 and 0.08 nM, respectively. The binding of this protein to cyclosporin A is negligible. Binding of tacrolimus to two commercial sources of ubiquitin, a bovine product, and a recombinant human ubiquitin, was also demonstrated after HPLC purification of the purchased preparations.

Amino Acid Sequence↗
PubMed2000

Analysis of the degradation of oligonucleotide strands during the freezing/thawing processes using MALDI-MS.

Synthetic oligonucleotide strands ranging from 5 to 25 units in length are commonly used as standards, probes, and templates in various bioanalytical applications. Until recently, their preparation, storage, and handling were regarded as unimportant, but this work provides valuable information to the contrary. The systematic degradation of oligonucleotide strands during sample preparation is investigated by repeatedly freezing/thawing short strands followed by matrix-assisted laser desorption ionization mass spectrometric (MALDI-MS) analysis. It is shown here that the longevity of an oligonucleotide strand is dependent on several factors including base composition, solution concentrations, and strand length as well as thawing conditions. Several trends in strand robustness were established. Our studies reveal that the robustness of strands is base-dependent: T-mer > A-mer > C-mer > G-mer. Likewise, an increase in the length of the strands increases the tendency of a sample to degrade. Another observation included that samples of mixed bases degrade according to structural conformations. All of these observations are attributed to the fact that the samples undergo degradation during sample/solvent isolation during freezing.

Base Sequence↗
PubMed2000

An Nkx-dependent enhancer regulates cGATA-6 gene expression during early stages of heart development.

The evolutionarily conserved GATA-6 transcription factor is an early and persistent marker of heart development in diverse vertebrate species. We previously found evidence for a functionally conserved heart-specific enhancer upstream of the chicken GATA-6 (cGATA-6) gene and in the present study we used transgenic mouse assays to further characterize this regulatory module. We show that this enhancer is activated in committed precursor cells within the cardiac crescent and that it remains active in essentially all cardiogenic cells through the linear heart stage. Although this enhancer can account for cGATA-6 gene expression early in the cardiogenic program, it is not able to maintain expression throughout the heart later in development. In particular, the enhancer is sequentially downregulated along the posterior to anterior axis, with activity becoming confined to outflow tract myocardium. Enhancers with similar properties have been shown to regulate the early heart-restricted expression of the mouse Nkx2.5 transcription factor gene. Whereas these Nkx2.5 enhancers are GATA-dependent, we show that the cGATA-6 enhancer is Nkx-dependent. We speculate that these enhancers are silenced to allow GATA-6 and Nkx2.5 gene expression to be governed by region-specific enhancers in the multichambered heart.

Animals↗
PubMed2000

Diabetes training for dietitians: needs assessment, program description, and effects on knowledge and problem solving.

Recent changes in management and medical nutrition therapy for diabetes mellitus have produced a need to retrain many practicing dietitians. To meet this need, a multidisciplinary group experienced in medical nutrition therapy and educational methods used a formal needs-assessment process to design a new training program. Sugar is Not a Poison (SNAP): The Dietitian's New Role in Diabetes Management is a 2 1/2-day program that uses written text, didactic presentation, and exercises that simulate patient encounters to accomplish 12 learning objectives. Program evaluations show high levels of participant satisfaction. Mean (+/- standard deviation) scores on pre- and postests of knowledge and problem solving were 69 +/- 13% and 86 +/- 9%, respectively (P < 0.01). The SNAP program needs assessment, training methods, and knowledge problem-solving test are relevant to all types of education programs in clinical dietetics.

Diabetes Mellitus↗