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Biomedical subjects

D L Edwards

Publications and source records attributed to D L Edwards.

At least 19 recordsLinked to original sources
PubMed2004

Effect of sperm concentration, medium osmolality and oocyte storage on artificial fertilisation success in a myobatrachid frog (Limnodynastes tasmaniensis).

The present study optimised artificial fertilisation and oocyte storage conditions in Limnodynastes tasmaniensis (Myobatrachidae). Data on general reproductive biology, the effect of sperm motility and concentration, medium osmolality and oocyte storage on artificial fertilisation success are presented. Egg number was most strongly correlated with bodyweight (r = 0.819). Sperm yield was correlated with testes weight (r = 0.827), which was strongly correlated with snout-vent length (r = 0.772). Optimal artificial fertilisation occurred in 0-7 mOsm kg(-1) amphibian Ringer, similar to ranid, bufonid and hylid species. High fertilisation rates were achieved using spermatozoa with little forwards progressive motility at comparatively low concentrations (3 x10(4) sperm cells mL(-1)) and with no relationship between percentage sperm motility and fertilisation success (correlation of fertilisation rate with sperm motility after activation: r = -0.145). Oocytes stored in 5 mOsm kg(-1) solutions showed no significant decline in fertilisability after 2 h, showing that swelling of the jelly surrounding the eggs does not prevent sperm from fusing with the oocyte in this species. Fertilisability of oocytes was extended to > 4 h in medium to high osmolality solutions (124-271 mOsm kg(-1)). These data allow for the future use of L. tasmaniensis in developing assisted reproductive technology protocols for foam-nesting myobatrachid species, many of which are now threatened with extinction in the wild.

Animals↗
PubMed2004

Evaluation of sampling locations for two radionuclide air-sampling systems based on the requirements of ANSI/HPS N13.1-1999.

The Pacific Northwest National Laboratory characterized the performance of sampling locations for two radionuclide air-sampling systems that continuously monitor radioactive air emissions from research and development facilities. The testing was conducted to determine whether sampling system locations would meet the criteria for uniform air velocity and contaminant concentration in the American National Standard Institute standard, Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stacks and Ducts of Nuclear Facilities (ANSI/HPS N13.1-1999). The standard is a revision of the 1969 version that the facilities have been required to meet. Whereas the 1969 standard provided prescriptive criteria for the selection of sampling locations, the 1999 standard is performance-based and requires well-mixed sampling locations that must be demonstrated through performance tests that are specified in the standard. Testing at the Life Sciences Laboratory I was performed on the existing stack at the current sampling location; a scale model was built and used in place of the Radiochemical Processing Laboratory. Although both facilities' sampling sites were compliant with the 1969 standard, only the Radiochemical Processing Laboratory met the criteria of the revised standard. In the future, the use of a computational fluid dynamics computer model may be useful in determining whether a sampling location is likely to test successfully.

Aerosols↗
PubMed2004

Results of inspection and cleaning of two radionuclide air-sampling systems based on the requirements of ANSI/HPS N13.1-1999.

The Pacific Northwest National Laboratory inspected and cleaned two radionuclide air-sampling systems that continuously monitor radioactive air emissions from research and development facilities. The inspection and cleaning was performed to evaluate effective methods and potential cost impacts of maintenance requirements in the revised American National Standard Institute standard Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stacks and Ducts of Nuclear Facilities. The standard requires at least annual inspections of sampling systems followed by cleaning if deposits are visible. During 2001 and 2002, inspections were performed leaving the sampling systems in place and inserting videoscope cables into different access points to allow viewing of the inside and outside of sampling manifolds and transport lines. Cleaning was performed on one of the systems by disconnecting and extracting the sampling manifold, then washing it with de-ionized water and scrub brushes. The wash water was analyzed for radioactivity and solids. Results of the inspection showed greater deposition in one of the systems than would be expected by a High Efficiency Particulate Air (HEPA) filtered exhaust stream, possibly due to accumulation of dust from a short period when unfiltered air was exhausted from construction areas. The second system was also downstream of HEPA filters and appeared much cleaner. The videoscope was a useful and cost-effective tool and provided a better view than could be obtained with the naked eye. However, because even small amounts of deposition were made visible with the videoscope, clarification is needed in defining when probe washing is merited, particularly in existing sampling systems whose design is not conducive to easy removal and cleaning.

Aerosols↗
PubMed1998

Uptake and reversibility of uptake of nickel by human macrophages.

The use of nickel-containing alloys in dentistry has been questioned because of the biological liabilities of nickel and the release of nickel ions from dental appliances into the oral cavity. The uptake of nickel by cells in the oral tissues is a critical factor in assessing the biological liabilities of nickel. Nickel uptake by macrophages may be particularly important because of the central role of macrophages in the inflammatory process and the known role of the macrophage in orchestrating the response to biomaterials. The aims of the current study were to assess the reversibility of the uptake of nickel from human macrophages and determine the portion of the nickel which reaches the nuclei as a function of time. Cellular nickel content was measured by means of atomic absorption spectrometry. Nuclear nickel content was assessed after fractionating cells. The results showed that nickel was rapidly taken up by macrophages and that the nickel accumulated in the nucleus in as little as 8 h. After 48 h, over 60% of the cellular nickel was in the nucleus. Once taken up, the nickel was lost at a lower rate. The rate of loss decreased as the initial exposure time to the nickel increased. Thus, the results indicated that macrophages may accumulate nickel if the time between exposures is insufficient to reverse the uptake. Further studies are necessary to correlate the retention of nickel with impaired function of macrophages and to further define the biological risks of using nickel in dental alloys.

Biological Availability↗
PubMed1997

Synthetic peptide combinatorial libraries: a method for the identification of bioactive peptides against phytopathogenic fungi.

Synthetic combinatorial libraries were evaluated with an iterative process to identify a hexapeptide with broadspectrum activity against selected phytopathogenic fungi. A D-amino acid hexapeptide (FRLKFH) and pentapeptide (FRLHF) exhibited activity against Fusarium oxysporum f. sp. lycopersici, Rhizoctonia solani (anastomosis group 1), Ceratocystis fagacearum, and Pythium ultimum. The peptides showed no hemolytic or mutagenic activity. Fluorescent microscopy studies with a membrane impermeant dye indicated that fungal cytoplasmic membranes were compromised rapidly and that the nuclear membrane was also affected.

Amino Acid Sequence↗
PubMed1996

Long-term nitric oxide blockade in the pregnant rat: effects on blood pressure and plasma levels of endothelin-1.

OBJECTIVE: Abnormalities in the production of nitric oxide and endothelin-1 have been implicated in the development of preeclampsia. We postulated that long-term nitric oxide synthase inhibition with L-nitro-arginine methyl ester would induce sustained hypertension, a rise in plasma levels of endothelin-1, and fetal growth restriction. STUDY DESIGN: Conscious virgin and pregnant Sprague-Dawley rats received infusions of vehicle or L-nitro-arginine methyl ester (2.5 mg/kg/hr) for 11 days. Mean arterial pressure was assessed serially. On day 21 of gestation (or equivalent in virgin rats) plasma was collected for endothelin-1 levels; pup weight and litter size were determined. Data were analyzed with analysis of variance and regression techniques. RESULTS: Mean arterial pressure was constant in virgin control rats (n = 7) but declined in pregnant control rats (n = 11) as gestation advanced. Nitric oxide synthase inhibition in virgin (n = 10) and pregnant (n = 11) rats caused sustained elevations in mean arterial pressure (165 +/- 7 vs 100 +/- 3 mm Hg, L-nitro-arginine methyl ester vs control virgin rats, p < 0.0001; 149 +/- 5 vs 91 +/- 2 mm Hg, L-nitro-arginine methyl ester vs control pregnant rats, p < 0.0001). L-nitro-arginine methyl ester induced a rise in plasma endothelin-1 levels in virgin (4.4 +/- 0.1 vs 3.5 +/- 0.1 pg/ml, L-nitro-arginine methyl ester vs control, p < 0.0001) and pregnant rats (3.0 +/- 0.1 vs 2.6 +/- 0.1 pg/ml, L-nitro-arginine methyl ester vs control, p < 0.0001). Pregnant rats had lower endothelin-1 levels than did virgin rats (p < 0.0001). Mean arterial pressure and endothelin-1 were significantly correlated in pregnant rats. L-nitro-arginine methyl ester decreased pup weight (2.4 +/- 0.4 vs 3.7 +/- 0.2 gm/pup/litter, L-nitro-arginine methyl ester vs control, p < 0.01) and litter size (6.6 +/- 1.3 vs 10.2 +/- 0.9 pups/litter, L-nitro-arginine methyl ester vs control, p < 0.05). CONCLUSIONS: Long-term nitric oxide synthase blockade causes sustained hypertension, elevated levels of endothelin-1, and fetal growth restriction. Although the endocrine and pressor effects are not unique to pregnancy, this model clearly induces some of the changes seen in preeclampsia and may be useful for studying specific interventions.

Animals↗
PubMed1996

Body consciousness, illness-related impairment, and patient adherence in hemodialysis.

Recent theory and evidence suggests that bodily self-focusing tendencies (e.g. private body consciousness) may be associated with medical regimen adherence among chronically ill patients. The present study examined the joint effects of private body consciousness and degree of illness-related physical impairment on treatment regimen adherence in a sample of 52 hemodialysis patients. It was predicted that the effect of PBC on adherence would vary as a function of patients' level of illness-related physical impairment. For patients experiencing more severe impairment, higher PBC scores were associated with poorer adherence to the prescribed medication and dietary regimen. In contrast, for patients experiencing a relatively low degree of disease-related physical impairment, higher private body consciousness was associated with more favorable adherence. Results are discussed in terms of self-focused attention and behavioral self-regulation theories. Implications for future research and clinical intervention are also discussed.

Activities of Daily Living↗
PubMed1990

Treatment of Kawasaki disease.

The epidemiology, etiology, diagnosis, and treatment of Kawasaki disease are reviewed. Kawasaki disease, or mucocutaneous lymph node syndrome, is an acute, usually self-limiting, multiple-organ-system disease of childhood that occurs both epidemically and endemically worldwide. The etiology of the disease is unknown but may involve an infectious agent. To be diagnosed, a patient must be febrile for at least five days and show four of five additional clinical features: bilateral conjunctivitis, changes in the oral mucosa, changes in the extremities, rash, and cervical lymphadenopathy. The most important complications are cardiac; patients may develop aneurysms or thrombosis of the coronary arteries or myocarditis. Other complications include arthritis, conjunctivitis, and hydrops of the gallbladder. Aspirin, intravenous immune globulin, corticosteroids, and antithrombotic agents have been investigated for use in the treatment of Kawasaki disease with varying results. Current recommendations suggest therapy with aspirin 80-100 mg/kg/day every six hours for the first 14 days after diagnosis and intravenous immune globulin 400 mg/kg/day for the first four days. The dose of aspirin should then be reduced and continued for six to eight weeks if no coronary artery abnormalities are present. Treatment guidelines for Kawasaki disease are being refined. Current evidence supports early use of aspirin and intravenous immune globulin to prevent cardiac complications.

Antithrombins↗
PubMed1988

Biosynthetic regulation of endogenous hamster insulin and exogenous rat insulin II in transfected HIT cells.

To investigate mechanisms underlying biosynthetic regulation of an insulin gene, the rat insulin II gene was introduced into hamster beta-cells (HIT) by cotransfection with the neomycin phosphotransferase-selectable marker. The insulin gene fragment was 2.2 kilobases (kb) in length and contained all exons, introns, and approximately 700 base pairs (bp) of 5'-flanking DNA and 300 bp of 3'-flanking DNA. The HIT cell was known to have endogenous hamster insulin production under regulation by glucose and dexamethasone. In a pool of stably transfected cells (HIT M62pR2), rat insulin II and hamster insulin were produced at comparable rates. Glucose (20 mM) stimulated cellular [3H]leucine labeling of both hamster insulin and rat insulin II by approximately twofold. Addition of 10(-6) M dexamethasone to media containing 11.1 mM glucose inhibited biosynthesis of both hamster insulin and rat insulin II by greater than 90%. Thus, with both positive and negative biosynthetic regulation, changes in the cellular labeling of exogenous rat insulin II were qualitatively and quantitatively similar to those of the endogenous hamster insulin. These data suggest that the 2.2-kb rat insulin II gene fragment contained sufficient information for both expression and apparently "normal" biosynthetic regulation of exogenous rat insulin II (when compared with endogenous hamster insulin) in response to glucose and dexamethasone.

Animals↗
PubMed1987

Evidence for leucine-enkephalin immunoreactive neurons in the medulla which project to spinal cord in squirrel monkey.

Rhodamine-labeled latex microsphere injections were combined with horseradish peroxidase immunohistochemistry in squirrel monkeys to reveal neurons in the medullary raphe and medial reticular formation which projected to spinal cord and were positive for leucine-enkephalin-like immunoreactivity. Double-labeled cells were found primarily in nucleus raphe magnus, the reticular nucleus magnocellularis, and the lateral reticular nucleus. These results provide evidence for a descending projection from enkephalin-containing cells of the rostral ventral medulla, a region which has been strongly implicated in antinociception.

Animals↗
PubMed1987

Morphology of pontomedullary raphe and reticular formation neurons in the brainstem of the cat: an intracellular HRP study.

In order to understand better the anatomical substrates underlying processing of sensory information, the cytoarchitecture of neurons in the pontomedullary raphe and reticular formation was investigated following intracellular injections of horseradish peroxidase in the cat. Raphe cells studied were located in the nucleus raphe magnus, nucleus raphe obscurus, and nucleus raphe pallidus. The most prominent type had a smooth, oval cell body and oval dendritic tree with dendrites extending laterally into the adjacent reticular formation. Two other raphe cell types, large cells with a dorsoventral orientation of both cell body and dendritic tree, and very small cells, were rarer. The primary dendritic orientation lay in the coronal plane for all three raphe cell types. Wispy, straight, or clublike spines were located on more distal regions of dendrites, although we also found spineless dendrites. Raphe cells lying near longitudinal fiber pathways exhibited bundling of dendrites around the passing axon fascicles. Reticular formation cells studied were located in the nucleus gigantocellularis, nucleus magnocellularis, nucleus paragigantocellularis dorsalis, and nucleus reticularis paramedianus. Two morphological types were found on the basis of dendritic branching patterns: sparsely branched and densely branched. Most reticular formation cells had round dendritic trees as viewed in the coronal plane and polygonal cell bodies that were medium to large in size. There was no correlation between reticular formation cell morphology and nuclear location. Spines were more common on the densely branched cells, but for both reticular cell types they were usually absent from cell bodies and proximal dendrites. Thus, by using the criteria of dendritic branching and arbor shape along with distance from the midline it was possible to identify raphe cells as distinct from reticular formation cells. In contrast, no morphological characteristics were found that would differentiate cells in the two major median reticular formation nuclei, gigantocellularis and magnocellularis.

Animals↗
PubMed1986

Amygdalospinal projections in the cat.

Spinal cord injections of rhodamine-labeled fluorescent latex microspheres in the cat resulted in retrograde labeling of a dense, well-defined group of neurons within the central nucleus of the amygdala and a modest number of neurons in the medial nucleus. Amygdalospinal neurons were found to be large cells of variable shape and orientation that were distributed bilaterally with an ipsilateral predominence.

Amygdala↗