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Biomedical subjects

J L Edwards

Publications and source records attributed to J L Edwards.

At least 19 recordsLinked to original sources
PubMed2005

Fertility aspects in yearling beef bulls grazing endophyte-infected tall fescue pastures.

During a 2-year study, yearling beef bulls were used to determine the effects of grazing on endophyte-infected tall fescue on endocrine profiles, semen quality and fertilisation potential. Bulls were allotted to graze tall fescue pastures infected with Neotyphodium coenophialum (E+; n = 20 per year) or Jesup/MaxQ (Pennington Seed, Atlanta, GA, USA; NTE; n = 10 per year). Bulls were grouped by scrotal circumference (SC), bodyweight (BW), breed composites and age to graze tall fescue pastures from mid-November until the end of June (within each year). Blood samples, BW, SC and rectal temperatures (RT) were collected every 14 days. Semen was collected from bulls every 60 days by electroejaculation and evaluated for motility and morphology. The developmental competence of oocytes fertilised in vitro with semen from respective treatments was determined. Bulls grazing E+ pastures had decreased BW gain (P < 0.01), increased overall RT (P < 0.01) and decreased prolactin (P < 0.01) compared with animals grazing NTE pastures. Neither percentage of normal sperm morphology nor motility differed between bulls grazed on the two pasture types. Semen from E+ bulls demonstrated decreased cleavage rates (P = 0.02) compared with semen from NTE bulls. However, development of cleaved embryos to the eight-cell and blastocyst stages did not differ between the two groups. In conclusion, semen from bulls grazing E+ tall fescue resulted in decreased cleavage rates in vitro, which may lower reproductive performance owing to reduced fertilisation ability.

Animal Feed↗
PubMed2005

Biofilm Formation by Neisseria gonorrhoeae.

Studies were performed in continuous-flow chambers to determine whether Neisseria gonorrhoeae could form a biofilm. Under these growth conditions, N. gonorrhoeae formed a biofilm with or without the addition of 10 microM sodium nitrite to the perfusion medium. Microscopic analysis of a 4-day growth of N. gonorrhoeae strain 1291 revealed evidence of a biofilm with organisms embedded in matrix, which was interlaced with water channels. N. gonorrhoeae strains MS11 and FA1090 were found to also form biofilms under the same growth conditions. Cryofield emission scanning electron microscopy and transmission electron microscopy confirmed that organisms were embedded in a continuous matrix with membranous structures spanning the biofilm. These studies also demonstrated that N. gonorrhoeae has the capability to form a matrix in the presence and absence of CMP-N-acetylneuraminic acid (CMP-Neu5Ac). Studies with monoclonal antibody 6B4 and the lectins soy bean agglutinin and Maackia amurensis indicated that the predominate terminal sugars in the biofilm matrix formed a lactosamine when the biofilm was grown in the absence of CMP-Neu5Ac and sialyllactosamine in the presence of CMP-Neu5Ac. N. gonorrhoeae strain 1291 formed a biofilm on primary urethral epithelial cells and cervical cells in culture without loss of viability of the epithelial cell layer. Our studies demonstrated that N. gonorrhoeae can form biofilms in continuous-flow chambers and on living cells. Studies of these biofilms may have implications for understanding asymptomatic gonococcal infection.

Biofilms↗
PubMed2005

Exposure to a physiologically relevant elevated temperature hastens in vitro maturation in bovine oocytes.

The objective of this study was to evaluate nuclear (progression to metaphase II) and cytoplasmic (translocation of cortical granules to the oolemma) maturation in control (38.5 degrees C) and heat-stressed (41.0 degrees C) oocytes. Hoechst staining indicated that a similar proportion of control and heat-stressed oocytes progressed to meta-phase II. More heat-stressed oocytes had type III cortical granule distribution suggesting that heat stress accelerated cytoplasmic maturation. The kinetics of nuclear maturation was examined in a second experiment in which a higher proportion of heat-stressed oocytes progressed to metaphase I by 8 h and arrested at meta-phase II at 16 and 18 h after placement into maturation medium. However, differences related to maturation temperature were no longer apparent by 21 h. Heat-induced alterations in kinetics of nuclear and cytoplasmic maturation prompted a third experiment to evaluate if earlier insemination of heat-stressed oocytes ameliorates heat-induced reductions in development. A significant temperature x insemination time interaction was noted when evaluating blastocyst development. Blastocyst development was reduced when heat-stressed oocytes were inseminated with sperm 24 h after placement into maturation medium compared with controls. In contrast, blastocyst development was similar to controls when heat-stressed oocytes were inseminated at 19 h. Based on this interaction, earlier insemination in vitro prevented heat-induced reductions in oocyte development. Collectively, these studies suggest a cumulative effect of heat stress to hasten in vitro maturation in bovine oocytes.

Animals↗
PubMed2004

Major histocompatibility antigen expression on the bovine placenta: its relationship to abnormal pregnancies and retained placenta.

In viviparous animals, regulation of expression of major histocompatibility complex (MHC) class I antigens by the trophoblast cells, which constitute the outermost layer of the placenta, seems to be critical for maternal immunological acceptance of an allogeneic fetus. Cattle are unusual in this regard, since the bovine trophoblast cells, in specific regions of the uterine/placental interface, normally express MHC class I antigens during the third trimester of gestation. This expression appears to be biologically relevant as MHC class I compatibility between a cow and her fetus has been associated with an increased incidence of placental retention. We have found significant differences in lymphocyte populations, cytokine production, and trophoblast cell apoptosis in the placentomes of MHC-compatible and -incompatible pregnancies at parturition. This suggests that maternal immunological recognition of fetal MHC class I proteins triggers an immune/inflammatory response that contributes to placental separation at parturition in cattle. Early in pregnancy, a complete shutdown of MHC class I expression by trophoblast cells appears to be critical for normal placental development and fetal survival. In bovine somatic cell nuclear transfer (SCNT) pregnancies, there is an extremely high rate of fetal loss between days 30 and 90 of pregnancy. We have shown that in bovine SCNT pregnancies, between days 34 and 63 of gestation, there is both abnormal expression of MHC class I antigens by trophoblast cells and an abnormal accumulation of lymphocytes within the uterine stroma. Consequently, it is likely that activation of the maternal mucosal immune system, within the uterus at the same time when placentomes are being established, interferes with the process of placentome development and leads to immune-mediated abortion. Our data suggest that bovine MHC-compatible pregnancies provide a unique model for studying regulation of the uterine immune system, as well as immune-mediated placental rejection.

Abortion, Veterinary↗
PubMed2004

Detrimental effects of prostaglandin F2alpha on preimplantation bovine embryos.

Two studies were performed to determine effects of prostaglandin F2alpha (PGF2alpha) on continued development of pre-compacted (in vitro-produced) and compacted (in vivo-derived) bovine embryos. In Experiment 1, pre-compacted embryos were placed in KSOM media supplemented with polyvinyl alcohol (0.3%) and assigned to the following treatments: (1) control; (2) PGF-1 (1 ng/mL PGF2alpha); (3) PGF-10 (10 ng/mL PGF2alpha); (4) PGF-100 (l00 ng/mL PGF2alpha); or (5) PGE-5 (5 ng/mL PGE2). Following 4 days of incubation in assigned treatments, continued development of pre-compacted embryos to blastocysts was reduced by addition of PGF2alpha in culture medium (P = 0.002). Development did not differ between control and PGE2 treatments (P > 0.10). In Experiment 2, compacted morula' s were placed in KSOM-PVA supplemented media and assigned to one of four treatments: (1) control; (2) PGF-0.1 (0.1 ng/mL PGF2alpha); (3) PGF-1 (1 ng/mL PGF2alpha); and (4) PGF-10 (10 ng/mL PGF2alpha). After 24h in culture, embryos were washed and placed in KSOM-BSA (0.5%) without PGF2alpha for an additional 48 h until assessment for development. Continued development of compacted morula to blastocyst was not affected by addition of PGF2alpha to the culture medium (P > 0.10). However, hatching rates of embryos cultured with PGF2alpha were lower (P = 0.05). In conclusion, it is suggested that PGF2alpha has a direct negative effect on continued embryonic development of pre-compacted and compacted bovine embryos.

Animals↗
PubMed2004

Boerhaave's syndrome: CT diagnosis.

Boerhaave's syndrome is the postemetic rupture of a normal oesophagus, the diagnosis of which is not always immediately apparent. We present here a case report which illustrates the value of computed tomography (CT) scanning in making this often difficult diagnosis.

Aged↗
PubMed2004

Using activity and milk yield as predictors of fresh cow disorders.

The objective was to determine whether daily walking activity and milk yields could be used as predictors of metabolic and digestive disorders early in lactation. Data were collected from 1996 through 1999 from 1445 dairy cows in 3 Florida herds. Walking activity, milk yield, and other measures were collected from a computerized dairy management system. Mixed models analysis was used for data on cows before their first detected estrus, as identified by difference in activity. Healthy cows were defined as those without any metabolic or digestive disorder during the prebreeding stage, whereas a sick cow had an occurrence of those disorders at any time during the prebreeding stage. Metabolic disorders were ketosis, retained placenta, and milk fever. Digestive disorders included displaced abomasum, indigestion, reduced feed intake, traumatic gastritis, acidosis, and bloat. Data from cows with known cases of ketosis, left displaced abomasum, and digestive disorders were analyzed to determine changes in activity and milk yield before those specific disorders were clinically diagnosed. Although walking activity was generally lower among sick cows, cows with ketosis, left displaced abomasum, and digestive disorders had higher than average activity 8, 9, and 8 d, respectively, before each diagnosed disorder. Daily milk yields of sick cows were approximately 15 kg/d less than milk yields of healthy cows. Milk yields were lower by 6, 7, and 5 d, respectively, before diagnoses of ketosis, left displaced abomasum, and digestive disorders. Cows with ketosis, left displaced abomasum, and general digestive disorders could possibly be detected about 5 to 6 d earlier than clinical diagnoses based on changes in daily walking activity and milk yield.

Abomasum↗
PubMed2004

Retinol improves development of bovine oocytes compromised by heat stress during maturation.

The objectives of this study were to evaluate: 1) effects of a physiologically relevant elevated temperature on in vitro development of maturing oocytes, 2) effects of retinol on in vitro development of maturing oocytes, and 3) effects of retinol to improve development of oocytes compromised by an elevated temperature. Bovine oocytes were matured for 24 h at 38.5 or 41.0 degrees C (first 12 h) in 0 or 5 microM retinol. After insemination, cleavage and blastocyst development were assessed on d 3 and 8, respectively. Temperature, retinol, and their interaction were included in the statistical model. Culture of oocytes at 41.0 degrees C decreased the proportion of 8- to 16-cell embryos and increased that of 2-cell embryos. In addition, culture at 41.0 degrees C decreased the ability of oocytes to develop to the blastocyst stage. Blastocysts derived from oocytes cultured at 41.0 degrees C had fewer total nuclei. In 3 of the 7 experimental replicates, effects of 41.0 degrees C to reduce blastocyst development were minimal (difference in the development of the control vs. heat stress group was <20%). To provide a more precise test of our hypothesis (retinol administration may improve development of oocytes compromised by heat stress), data were analyzed, including only those replicates (n = 4) in which heat stress reduced development to blastocyst >20%. When this was done, a significant temperature x retinol interaction was noted. The addition of retinol to the maturation medium prevented heat-induced reductions in development of oocytes to blastocyst stage. Results indicate that retinol may protect oocytes from some of the deleterious effects of heat stress.

Animals↗
PubMed2003

Fatigue in adolescents with and following a cancer diagnosis: developing an evidence base for practice.

Although fatigue has been a focus for research in adult cancer care for some time, the same cannot be said for adolescent oncology practice. This paper summarises the literature concerning fatigue in adolescents with, and following, cancer diagnoses, drawing on data from four empirical studies. Fatigue is multidimensional, multifactorial and highly subjective, but can be managed to enhance self-caring and coping strategies. All of the studies reviewed within indicate that fatigue is a troublesome symptom, which impacts on quality of life. From this review, we set up a research study. This paper provides a brief report of preliminary data from this study drawn from a group of adolescents in late remission from childhood cancer. These data are used to evaluate the utility of focus groups as a method of data collection in exploring the concept of fatigue in adolescents. Concurring with the studies we reviewed, findings from the preliminary data suggest that fatigue is a highly subjective and 'abnormal' phenomenon that holds a variety of implied meanings and associated metaphors connected with past experiences of childhood cancer. The focus group proved to be a viable research method to facilitate mutual disclosure and provoke discussion. Recognition of the research challenges with adolescents, where there is the potential for a range of meanings for the experience of fatigue, is an important finding for future studies.

Adaptation, Psychological↗
PubMed2003

Cloning adult farm animals: a review of the possibilities and problems associated with somatic cell nuclear transfer.

In 1997, Wilmut et al. announced the birth of Dolly, the first ever clone of an adult animal. To date, adult sheep, goats, cattle, mice, pigs, cats and rabbits have been cloned using somatic cell nuclear transfer. The ultimate challenge of cloning procedures is to reprogram the somatic cell nucleus for development of the early embryo. The cell type of choice for reprogramming the somatic nucleus is an enucleated oocyte. Given that somatic cells are easily obtained from adult animals, cultured in the laboratory and then genetically modified, cloning procedures are ideal for introducing specific genetic modifications in farm animals. Genetic modification of farm animals provides a means of studying genes involved in a variety of biological systems and disease processes. Moreover, genetically modified farm animals have created a new form of 'pharming' whereby farm animals serve as bioreactors for production of pharmaceuticals or organ donors. A major limitation of cloning procedures is the extreme inefficiency for producing live offspring. Dolly was the only live offspring produced after 277 attempts. Similar inefficiencies for cloning adult animals of other species have been described by others. Many factors related to cloning procedures and culture environment contribute to the death of clones, both in the embryonic and fetal periods as well as during neonatal life. Extreme inefficiencies of this magnitude, along with the fact that death of the surrogate may occur, continue to raise great concerns with cloning humans.

Animals↗
PubMed2003

Alkaline phosphatase activity in bovine oocytes and preimplantation embryos as affected by removal of the zona pellucida and culture medium constituents.

The aims of the present study were: (1) to characterize alkaline phosphatase (AP) activity in bovine oocytes and embryos with intact or removed zona pellucida (ZP); and (2) to evaluate the effect of culture medium constituents on AP activity. Alkaline phosphatase activity in non-matured and matured oocytes was most evident nearest the plasma membrane and perivitelline space. In more than 90% of two- to 16-cell embryos, AP activity was observed in the perivitelline space and at blastomere contacts. In blastocysts, AP activity was localized to the trophectoderm. Only after immunodissection was AP activity detected in the inner cell mass. Removal of the ZP by pronase or mechanical means reduced AP activity. Alkaline phosphatase activity was detected in evacuated ZP after mechanical removal. Specific constituents comprising the embryo culture medium altered AP activity. Alkaline phosphatase activity was reduced in eight- to 16-cell embryos and evacuated ZP cultured in CR1aa + 0.4% bovine serum albumin compared with embryos cultured in CR1aa alone or embryos co-cultured on a monolayer of Buffalo rat liver cells in the presence of 10% fetal bovine serum. The presence of AP activity at blastomere contacts and in evacuated ZP limits its usefulness as a marker for the differentiation of embryonic cells comprising the early cleavage-stage embryo.

Alkaline Phosphatase↗
PubMed2001

Responsiveness of early embryos to environmental insults: potential protective roles of HSP70 and glutathione.

Early embryos are not as passive as previously thought. In the bovine, embryos as early as the 2-cell stage can respond to environmental insults at both the cellular and molecular level by altering expression of specific genes and synthesis of proteins. Moreover, sex related differences exist in how early embryos respond to otherwise hostile environments. As aggressive as early embryos may be to tolerate environment insults, the majority will fail to continue in development. Reduced developmental potential of embryos exposed to elevated temperatures is likely due to direct effects on the early embryo. However, as embryos proceed in development they acquire the ability to better withstand environmental insults. Developmental acquisition of tolerance to environmental stress may be contingent upon acquisition of protective biochemical mechanisms or simply due to increased cell numbers. Correlative evidence has suggested a potential role of heat shock protein 70 and glutathione for protection of embryos in face of elevated temperature. Of these two possibilities, HSP70 appears least likely to play a significant role in developmental acquisition of thermotolerance. Bovine embryos as early as the 2-cell stage, are able to mount a heat shock response; a developmental stage that is most sensitive to elevated temperatures. A more likely candidate for conferring increased resistance of early embryos to elevated temperature is glutathione.

Animals↗
PubMed2001

The role of complement receptor 3 (CR3) in Neisseria gonorrhoeae infection of human cervical epithelia.

Neisseria gonorrhoeae is an important sexually transmitted pathogen and a major cofactor in HIV-1 infection. This organism uses different mechanisms to infect male and female genital tract epithelia. Receptor-mediated endocytosis of N. gonorrhoeae is the principle mechanism of entry into male urethral epithelial cells. Infection in men leads to a pronounced inflammatory response. In contrast, N. gonorrhoeae infection in women induces ruffling of the cervical epithelia, allowing a macropinocytic mechanism of entry. Infection in women is frequently asymptomatic, suggesting suppression of the inflammatory response. N. gonorrhoeae-induced membrane ruffling and inflammation suppression are consistent with the ability of this bacterium to enter cervical epithelial cells, in vitro and in vivo, by interaction with complement receptor 3 (CR3), a receptor that does not trigger an inflammatory response. This receptor is present on cervical epithelial cells but not on male urogenital tract epithelia. N. gonorrhoeae engagement of CR3 initiates a unique mechanism of bacterial-induced membrane ruffling and internalization. These studies explain why the pathology of N. gonorrhoeae infection differs between males and females. Additionally, the observation that this receptor is present on cervical epithelia may provide insight into the pathogenesis of other sexually transmitted pathogens.

Animals↗
PubMed2001

Accuracy of recorded birth and calving dates of dairy cattle in the United States.

Frequencies of births that were reported for specific days of the month were documented for US dairy cattle born since 1987 by birth year, herd size, and registry status and compared with calving frequencies for those dates. Because birth dates are expected to be random and uniformly distributed throughout each month, percentages of births on individual dates were expected to be equal (3.3% for d 1 to d 28, 3.2% for d 29, 3.0% for d 30, and 1.9% for d 31). However, percentages of reported birth dates for d 1, 2, 10, 15, and 20 were higher than expected. The percentage of reported births for d 1 was highest (5.3%) of all days of the month regardless of herd size or registry status. The nonuniform distribution of birth dates within month indicated that a substantial number of birth dates were unknown and that estimated birth dates had been reported. About one-third of the birth dates recorded on d 1 appeared to have been estimated, or altered to gain an advantage in cattle shows. The highest frequencies for birth dates on d 1 (5.9 to 7.4%) were found for registered cows during months that initiated age groupings for dairy shows (March, June, September, and December). Birth dates for some registered cows were intentionally misreported as confirmed by comparison of birth dates of individual cows with calving dates of their dams. Reported calving dates appeared to be more accurate than reported births; the inflated frequency of recorded calvings on d 1 was only about 30% as large as the inflated frequency of recorded births. Because cow age is determined by birth date, proper reporting of birth dates is important to ensure the accuracy of standardized yield and fitness records and the genetic evaluations that are based on those records. When animals' recorded birth dates and their dams' calving dates differ, more credence should be given to the latter to improve accuracy.

Age Distribution↗
PubMed2000

Interoperability of biodiversity databases: biodiversity information on every desktop.

Data about biodiversity are either scattered in many databases or reside on paper or other media not amenable to interactive searching. The Global Biodiversity Information Facility (GBIF) is a framework for facilitating the digitization of biodiversity data and for making interoperable an as-yet-unknown number of biodiversity databases that are distributed around the globe. In concert with other existing efforts, GBIF will catalyze the completion of a Catalog of the Names of Known Organisms and will develop search engines to mine the vast quantities of biodiversity data. It will be an outstanding tool for scientists, natural resource managers, and policy-makers.

Animals↗
PubMed2000

Effects of mental stress on brachial artery flow-mediated vasodilation in healthy normal individuals.

BACKGROUND: Mental stress is associated with increased risk for cardiovascular events, possibly because of acute increases in endogenous catecholamines. Recently, brachial artery flow-mediated vasodilation has been used for noninvasive assessment of macrovascular endothelial function. The effect of mental stress and its associated changes in sympathetic activation on brachial artery endothelium-dependent vasomotor tone in vivo remains unknown. METHODS AND RESULTS: Two-dimensional ultrasound was used to measure brachial artery flow-mediated vasodilation before and after mental stress (provoked by a standard arithmetic challenge) in 21 healthy individuals (10 men, 11 women; average age 23.5 years). The flow stimulus resulted from a 3-minute cuff occlusion of distal forearm blood flow, causing distal hyperemia and a transient 2- to 3-fold increase in brachial artery blood flow on cuff release. During mental stress, heart rate increased on average by 29.6% and blood pressure increased on average by 17.9%. The sympathetic stimulus resulted in a 64% average increase in flow-mediated vasodilator response (P <.001). The enhanced vasodilator response during mental stress was similar for men and women. CONCLUSIONS: Mental stress can have marked effects on endothelium-dependent, flow-mediated vasodilation in healthy, normal individuals. Similar studies in individuals with impaired endothelial function may further our understanding of the role of mental stress in the development of cardiovascular events.

Adult↗
PubMed2000

Ultrastructural and karyotypic examination of in vitro produced bovine embryos developed in the sheep uterus.

This study examined whether development of bovine in vitro produced (IVP) blastocysts in the sheep uterus resulted in morphologically and karyotypically normal elongation stage bovine blastocysts. Seven day IVP bovine blastocysts, resulting from either in vitro maturation and fertilization, nuclear transfer (NT), or parthenogenic activation, were surgically transferred at the blastocyst stage into sheep uteri. Sheep were sacrificed after 7-9 days, and blastocysts were flushed from their uteri. One of each kind of IVP bovine blastocyst was recovered from sheep uteri for analysis by transmission electron microscopy, and nine NT blastocysts were used to establish cell cultures that were analysed for chromosome complement. TEM analysis of in vivo-derived elongation stage bovine and ovine blastocysts was done for comparative purposes. Most ultrastructural features of the 13-19 day blastocysts were similar to earlier stage blastocysts except that distinct alternative mitochondrial morphologies were found between epiblast and trophectoderm cells. Monociliated cells, presumably nodal cells, were observed in the bovine epiblast and hypoblast, and retrovirus-like particles were elaborated by cells in these same areas. Development in the sheep uterus of IVP bovine blastocysts resulted in the presence of crystalloid bodies in the trophectoderm cells, and apoptotic and necrotic cells were observed in the epiblast tissue. Thus, in vivo incubation in the sheep uterus allowed nearly normal development to the elongated blastocyst stage and may be useful for assessment of NT bovine blastocyst developmental competence. Cell cultures derived from the NT blastocysts had normal chromosome complements suggesting that activation by ionomycin and 6-dimethyl-aminopurine did not cause detrimental changes in ploidy in those blastocysts that developed.

Animals↗