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Biomedical subjects

D W Stanley

Publications and source records attributed to D W Stanley.

At least 19 recordsLinked to original sources
PubMed2001

Prostaglandin biosynthesis by fat body from true armyworms, Pseudaletia unipuncta.

We describe prostaglandin (PG) biosynthesis by microsomal-enriched fractions of fat body prepared from true armyworms, Pseudaletia unipuncta. PG biosynthesis was sensitive to experimental conditions, including incubation time, temperature, pH, substrate and protein concentration. Optimal PG biosynthesis conditions included 1 mg of microsomal-enriched protein, incubated at 28 degrees C for 7.5 min at pH 8. These preparations yielded four major PGs: PGA(2), PGE(2), PGD(2) and PGF(2alpha). PGA(2) and PGE(2) were the predominant eicosanoids produced under these conditions. Two non-steroidal anti-inflammatory drugs, indomethacin and naproxen, effectively inhibited PG biosynthesis. Unlike other invertebrate PG biosynthetic systems studied so far, the true armyworm system appeared to be independent of the usual exogenous co-factors required by mammalian and other invertebrate systems. These findings are discussed with respect to PG biosynthesis in other invertebrate and vertebrate systems.

Animals↗
PubMed2001

Innate immune reactions stimulated by a lipopolysaccharide-like component of the alga Prototheca (strain 289).

We report on the influence of an LPS-like molecule (aLPS) from the pathogenic alga, Prototheca (strain 289) on insect and murine innate immune reactions. Insect innate reactions to infection include nodule formation, a process of entrapping bacterial cells in aggregates of hemocytes. We recorded eicosanoid-dependent, dose-related nodulation reactions to aLPS in hornworms (Manduca sexta). The insect reaction was attenuated by pre-incubating the aLPS with polymyxin-B. Conversely, the murine macrophages reacted to challenge with Escherichia coli LPS by secreting cytokines, but did not react to aLPS. We infer that, while highly conserved with respect to intracellular mechanisms of interaction, insect and mammalian immune surveillance systems differ in recognition of LPS molecular types.

Animals↗
PubMed2001

Long-term changes in watershed nutrient inputs and riverine exports in the Neuse River, North Carolina.

We compared patterns of historical watershed nutrient inputs with in-river nutrient loads for the Neuse River, NC. Basin-wide sources of both nitrogen and phosphorus have increased substantially during the past century, marked by a sharp increase in the last 10 years resulting from an intensification of animal production. However, this recent increase is not reflected in changes in river loading over the last 20 years. Temporal patterns in river loads more closely parallel short-term changes in point sources and cropland nutrient application despite their overall lower magnitude. Total phosphorus loads have declined at all stations considered, corresponding to a 1988 phosphate detergent ban. Nitrogen load temporal patterns vary by location and the nitrogen fraction considered. The furthest upstream station exhibited nitrogen decreases after the completion of a dam in 1983. At a station just downstream of a rapidly growing urban area, the total nitrogen load has increased since the mid-1980s, primarily as a nitrate concentration increase. This is consistent with concurrent increases in chemical fertilizer use and point source discharges, as well as increased nitrification at treatment plants. This increase in nitrate loading is not reflected at the most downstream station, where no clear nitrogen trends are discernable. The lack of clear downstream nutrient increases suggests that current water quality impairment in the lower river and estuary may result from chronic nutrient overload rather than recent changes in the watershed. If this is true, then the impact of a planned 30% nitrogen loading reduction may not be immediately apparent. We calculate that, given annual variability, detecting a load reduction of this magnitude will take at least four years, and, should nutrients accumulated in the watershed become a significant source, detecting the resulting ecological improvements is likely to take substantially longer.

Fresh Water↗
PubMed2001

Arachidonic and eicosapentaenoic acids in tissues of the firefly, Photinus pyralis (Insecta: Coleoptera).

We report on the presence of high proportions of arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) in the tissue lipids of adult fireflies, Photinus pyralis. Arachidonic acid typically occurs in very small proportions in phospholipids (PLs) of terrestrial insects, ranging from no more than traces to less than 1% of PL fatty acids, while 20:5n-3 is often missing entirely from insect lipids. Contrarily, 20:4n-6 made up approximately 21% of the PL fatty acids prepared from whole males and females, and from heads and thoraces prepared from males. Proportions of 20:4n-6 associated with PLs varied among tissues, including approximately 8% for male gut epithelia, 13% for testes, and approximately 25% for light organs and body fat from males. Substantial proportions of 20:5n-3 were also associated with PLs prepared from male firefly tissues, including 5% for body fat and 8% for light organs. Because 20:4n-6 and 20:5n-3 are precursors for biosynthesis of prostaglandins and other eicosanoids, we considered the possibility that firefly tissues might produce eicosanoids at exceptionally high rates. Preliminary experiments indicated otherwise. Hence, fireflies are peculiar among terrestrial insects with respect to maintaining high proportions of PL 20:4n-6 and 20:5n-3.

Animals↗
PubMed2001

Eicosanoids act in nodulation reactions to bacterial infections in newly emerged adult honey bees, Apis mellifera, but not in older foragers.

Nodulation is the first, and qualitatively predominant, cellular defense reaction to bacterial infections in insects. We tested the hypothesis that eicosanoids also mediate nodulation reactions to bacterial challenge in adults of a social insect, the honey bee, Apis mellifera. Treating newly-emerged experimental bees with the eicosanoid biosynthesis inhibitor, dexamethasone, impaired nodulation reactions to bacterial infections, and the influence of dexamethasone was reversed by treating infected insects with arachidonic acid, an eicosanoid precursor. Several other eicosanoid biosynthesis inhibitors, including the cyclooxygenase inhibitor, indomethacin, and the dual cyclooxygenase/lipoxygenase inhibitor, phenidone, also impaired the ability of experimental honeybees to form nodules in reaction to bacterial challenge. The influence of phenidone on nodulation was expressed in a dose-dependent manner. However, in experiments with older honey bees foragers, similar bacterial challenge did not evoke nodulation reactions. We infer from our results that while eicosanoids mediate cellular immune responses to bacterial infections in newly emerged honey bees, and more broadly, in most insect species, nodulation reactions to bacterial challenge probably do not occur in all phases of insect life cycles.

Abdomen↗
PubMed2000

Anoxia tolerance of con-familial tiger beetle larvae is associated with differences in energy flow and anaerobiosis.

In this study, we compared survivorship, heat dissipation and biochemical features of anaerobiosis of two tiger beetle species (Coleoptera: Cicindelidae) exposed to anoxia. One species commonly experiences environmental immersion from rainfall and snowmelt (Cicindela togata), and the habitat of the other (Amblycheila cylindriformis) is not prone to flooding. The ancestral genus, A. cylindriformis, survives anoxia for only 2 days at 25 degrees C. In response to anoxia, these larvae immediately lose locomotory abilities, tissue concentrations of ATP fall precipitously within 12 h, and significant amounts of lactate are quickly produced. In contrast, C. togata larvae tolerate anoxia for 5 days. Heat dissipation is downregulated to a greater degree than that seen in A. cylindriformis (3.4% versus 14% of standard normoxic rate, respectively), the ability for locomotion is maintained and normoxic levels of ATP are defended for at least 24 h. Lactate is not accumulated until well into anoxic bout, and significant amounts of alanine are also produced. This study provides evidence that tiger beetles differ in physiological responses to anoxia, and that these differences are correlated with flooding risk and with species distribution.

Adaptation, Physiological↗
PubMed1999

Eicosanoids mediate nodulation reactions to bacterial infections in larvae of the butterfly, Colias eurytheme.

Nodulation is the first, and qualitatively predominant, cellular defense reaction to bacterial infections in insects. Treating larvae of the butterfly Colias eurytheme with the eicosanoid biosynthesis inhibitor dexamethasone, strongly impaired nodulation reactions to bacterial infections. The influence of dexamethasone was reversed by treating infected insects with arachidonic acid, an eicosanoid precursor. An eicosanoid biosynthesis system in C. eurytheme larvae is documented. Specifically, the presence of eicosanoid-precursor polyunsaturated fatty acids in tissue phospholipids was determined, an intracellular phospholipase A2 that can release arachidonic acid from tissue phospholipids was recorded, and eicosanoid biosynthesis, registered as conversion of exogenous radioactive 20:4n-6 into eicosanoids, was observed. These findings support the hypothesis that eicosanoids mediate cellular immune responses to bacterial infections in these butterfly larvae, and more broadly, in most, if not all, insects.

Animals↗
PubMed1991

Biological membrane deterioration and associated quality losses in food tissues.

Biological membranes are rarely considered by food scientists when the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yet, membranes and their deterioration play a major but underestimated role in food losses, and recent biochemical information indicates that at least some of these reactions can be controlled by procedures suited to food materials. Much of the present information available on membrane degradation in food systems is incomplete and speculative. It is known, however, that in order to accomplish their many indispensable functions in cells, membranes are constituted mainly of phospholipids, protein, and some carbohydrates arranged in thin, bimolecular sheet-like structures that serve to compartmentalize cells and their organelles. Membranes have embedded in their asymmetric surfaces complements of catalytic and cytoskeletal proteins that serve permeability and structural functions. Membrane surfaces exhibit fluidity, due partially to the continuous lateral diffusion of lipids and some proteins. Two important consequences of fluidity are the ability of membrane phospholipids to exist in different interconvertible conformational phase structures and the formation of heterogenous lipid domains on the membrane surface. Cellular death leads unavoidably to the initiation of membrane deterioration. While the time course of this series of reactions differs in animal and plant tissue, they are damaged by generally similar mechanisms. These include an initial peroxidative attack on polyunsaturated fatty acids, with the concomitant production of free radicals. Many biological agents can act as accelerating agents in these reactions, including transition metal ions, heme compounds, radiation, illuminated chlorophyll, calcium, and ethylene. Once formed, free radicals catalyze further reactions that can affect all aspects of membrane function and cellular metabolism, and lead ultimately to significant losses in food quality through defects such as chilling injury and cold shortening. These are aggravated by many food-processing steps, especially those that involve tissue disruption. Control of membrane breakdown by exogenous chemical intervention has been practiced, but, at best, this only slows the rate of these reactions. Newer approaches to this problem include dietary treatment of meat animals, modified storage and packaging conditions, and genetic interventions. This review advances the proposition that membrane deterioration can be considered a "universal mechanism" that leads to significant quality losses in food. Perhaps because the study of biological membranes and the biochemical and physiological properties has only begun recently, not much progress has been made in finding practical control mechanisms for these reactions in food systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Quick-freeze differential scanning calorimetry and saturation transfer electron spin resonance: novel techniques for assessing phase transitions in biological membranes.

Quick-freeze differential scanning calorimetry (QF-DSC) and saturation transfer-electron spin resonance (ST-ESR) spectroscopy were used to study lipid gel-phase transitions in mature green tomato fruit microsomal membranes. ST-ESR of 12-doxyl methyl stearate labelled membranes proved to be reproducible and provided increased sensitivity to temperature-induced structural changes, allowing the detection of several transitions in isolated membranes (6 degrees C, 21 degrees C, 28 degrees C). QF-DSC led to the assessment of lipid gel phase transitions in isolated microsomal membranes and microsomal membrane lipids by enhancing the transition. A phase transition enthalpy of 114 J/g and an onset temperature of 29.8 degrees C were obtained for whole membranes while with isolated lipids values of 370 J/g and 19.9 degrees C were found.

Calorimetry, Differential Scanning↗
PubMed1981

Preparation of muscle samples for electron microscopy.

The relevant literature on EM preparation techniques for muscle is reviewed. The currently available methodologies are presented and critically discussed from the point of view of the biologist and the food scientist. Those SEM and TEM procedures which have proved to be most useful in the present state of the art of specimen preparation for EM are summarized. Some of the more recently available staining and fracturing procedures for muscle, as well as specimen preparation procedures for intermicroscopic (LM, SEM, TEM) correlation are stressed. It is proposed that the normal ultrastructural appearance of muscle should serve as a baseline for the ultrastructural examination of meat.

Animals↗
PubMed1975

Alleviating mortality associated with a vitamin E-selenium deficiency by dietary ascorbic acid.

Adding ascorbic acid to a practical ration deficient in vitamin E and selenium for the growing duck substantially reduced associated mortality. The continued appearance of various myopathies but absence of vascular faults supported implication of a reduced de novo ascorbate synthesis as part of the syndrome. Presumably, alleviation of this induced secondary inadequacy with its more lethal pathology was the primary reason for the lower death rate.

Animal Feed↗