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Biomedical subjects

S Mayo

Publications and source records attributed to S Mayo.

17 recordsLinked to original sources
PubMed2004

Impact of chronic catheterization and automated blood sampling (Accusampler) on serum corticosterone and fecal immunoreactive corticosterone metabolites and immunoglobulin A in male rats.

Jugular catheters were inserted in nine male rats under general isofluorane anesthesia and the catheters were connected to a commercially available computerized blood sampling device (Accusampler). Blood samples (150 microl) were collected every 4 h during the first 24 h after surgery and every 12 h during the following 72 h until 94 h after surgery, when the animals were killed. All fecal pellets were collected at blood sampling. Serum corticosterone and fecal concentrations of immunoreactive corticosterone metabolites and immunoglobulin A (IgA) were quantified by ELISAs. In blood, high corticosterone concentrations (>200 ng/ml) were recorded in the first samples obtained after surgery, but the concentrations decreased steadily during the day and became cyclical, showing a diurnal variation with high levels during evenings and low levels in the mornings. The automatic blood sampling itself did not result in recordable increases in serum corticosterone concentrations. The time delay between the presence of elevated corticosterone levels in blood and in feces was approximately 12 h. Fecal immunoreactive corticosterone metabolite levels remained elevated during the 94 h study period after surgery. The fecal concentrations of IgA showed substantial between-animal variation and decreased non-significantly after the surgery. Like serum corticosterone, fecal IgA showed a diurnal variation in amounts excreted, in this case with high values in the morning and low values in the evening. The concentrations of fecal corticosterone and IgA were negatively correlated in samples obtained before surgery but no correlation existed after surgery. This indicates that fecal immunoreactive corticosterone metabolites, but not IgA, constitute a good marker of acute stress. For immunoreactive corticosterone metabolites as well as for IgA, the concentration in feces correlated well with total excretion, making single fecal samplings usable as a measure of total secretion.

Acute Disease↗
PubMed2002

Development of a diphasic dialysis method for the extraction/purification of residues of ethinylestradiol in hair of cattle, and determination by gas chromatography-tandem mass spectrometry.

A confirmatory method for the analysis of ethinylestradiol extracted from cattle hair was developed. After the extraction of the xenobiotic from the hair, by using alkaline digestion, the purification of the extract was carried out by employing diphasic dialysis. For the optimization of the technique several parameters was evaluated such as pH, extraction solvents, temperatures, times and agitation speeds. The detection and confirmation of the steroid was accomplished by using a GC-MS2 ion trap system after trimethylsilylation. The calibration curve was linear over the range of 4-20 ng/g. The detection and quantification limit were 0.52 and 0.80 ng/g respectively; with recoveries up to 94%.

Animals↗
PubMed2001

Quantitative in-line phase-contrast imaging with multienergy X rays.

We present a new method for quantitative nondestructive characterization of objects by x-ray phase-contrast imaging. Spatial distributions of the projected values of the complex refractive index in the sample are reconstructed by processing near-field images collected at a fixed sample-to-detector distance using a polychromatic incident beam and an energy-sensitive area detector, such as a CCD used in the photon-counting spectroscopy mode. The method has the potential advantages of decreased radiation dose and increased accuracy compared to conventional techniques of x-ray imaging.

Journal Article↗
PubMed2000

Chemiluminescence detection of nine corticosteroids in liver.

A method for the determination of nine corticosteroids in bovine liver was developed. The liquid-liquid extraction method consisted in the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract was evaporated to dryness and the residue redissolved in acetonitrile. The removal of fats was performed with n-hexane and the acetonitrile layer was evaporated. Afterwards, analysis of the extracts was performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as reagent. The recovery curves, performed at five spiking levels (different for each corticosteroid), showed that recoveries of at least 70.5% could be obtained from liver. The chemiluminescence detection gave satisfactory results with respect to sensitivity, and the LOQ ranged from 0.13 ppb for prednisolone to 8.40 ppb for betamethasone. The maximum mean RSD was 4.8% and 7.3% for intra- and inter-day assay, respectively.

Animals↗
PubMed1999

Determination of dexamethasone in bovine liver by chemiluminescence high-performance liquid chromatography.

A new method for the determination of dexamethasone (9alpha-fluoro-11beta,17alpha,21-trihydroxy-16alpha -methylpregna-1, 4-diene-3,20-dione) in bovine liver was developed. This new liquid-liquid extraction method comprises the addition of sodium hydroxide to the tissue sample followed by extraction with ethyl acetate. After centrifugation, the extract is evaporated to dryness and the residue dissolved in acetonitrile. The cleaning of the fat is performed with n-hexane, and the acetonitrile layer is evaporated. Analysis of the extracts is performed using high-performance liquid chromatography with chemiluminescence detection employing luminol as CL reagent. A series of recovery curves performed at spiking levels of 50, 30, 10, 5, and 2.5 ppb show that at least 80% of DEX can be recovered from liver and that the chemiluminescence detection yields satisfactory results with respect to sensitivity (LOD 0.2 ppb), reproducibility (CV% 10.7) and repeatability (CV% 6.2-8.9).

Animals↗
PubMed1994

Central alpha-adrenergic involvement in morphine-mediated suppression of splenic natural killer activity.

Alpha 1-adrenergic pathways are involved in morphine-induced suppression of murine splenic NK activity. To investigate the level of involvement following morphine administration, the peripheral acting alpha-adrenoceptor antagonist doxazosin and the broad acting alpha-adrenoceptor antagonist phentolamine were employed. Mice preadministered phentolamine (2.0 mg/kg) exhibited a modest but insignificant suppression of splenic NK activity following morphine administration while mice preadministered doxazosin (1.0 mg/kg) or vehicle showed a significant decrease in splenic NK activity following morphine administration. Morphine was also found to significantly (P < 0.01) increase splenic serotonin levels (14.88 +/- 1.62 ng/mg) relative to saline-treated controls (7.3 +/- 0.9 ng/mg). Both phentolamine and doxazosin pretreatment completely or partially blocked morphine-mediated elevation of splenic serotonin levels, respectively. Morphine administration decreased the ability of NK cells to form conjugates with target (YAC-1 lymphoma) cells and decreased the number of active killer cells within the conjugate population. Collectively, these results implicate central alpha-adrenergic involvement following acute morphine administration in suppressing splenic NK activity indirectly through a reduction in the number of effector-target conjugates and active cytolytic effector cells.

Animals↗
PubMed1993

Characterization of a (+)-azidophenazocine-sensitive sigma receptor on splenic lymphocytes.

A study was undertaken to structurally define and functionally assess sigma receptors on splenocytes using the highly selective sigma ligand (+)-azidophenazocine. Radioreceptor assays under reduced lighting show (+)-azidophenazocine can effectively block the binding of sigma ligands [3H]haloperidol (IC50 = 30 nM, Ki = 19.0 nM) and [3H](+)-pentazocine (IC50 = 40 nM, Ki = 350 nM), but not the dopamine (D2) ligand [3H]spiperone (IC50 > 5 microM) to splenic lymphocytes. [3H](+)-1-Propyl-3-(3-hydroxyphenyl)piperidine ([3H](+)-PPP) sites (Kd = 40.8 nM, Bmax = 2.32 pmol/mg) were also present on these lymphocytes. Additional studies using [3H](+)-azidophenazocine indicated the presence of saturable sites (Kd = 29.7 nM, Bmax = 760 fmol/mg) on splenic lymphocytes. There are no significant differences in affinity between sites found on T-enriched (Kd = 59 +/- 47 nM) and B-enriched lymphocytes (Kd = 23 +/- 5 nM). Photoaffinity labeling studies of splenocyte membranes with [3H](+)-azidophenazocine revealed a protein migrating at an apparent m.w. of 57 kDa under reducing and nonreducing conditions on SDS-PAGE. The labeling was specific because pretreatment with unlabeled haloperidol, (+)-PPP, 1,3 di(2-tolyl)guanidine, (+)-pentazocine, and (+)-azidophenazocine before cross-linking competed away > 75% of the radioactivity associated with the protein, whereas (-)-pentazocine and naloxone were significantly less effective. This data together with the observation that both (+)-azidophenazocine or haloperidol inhibit Con A-induced production of IFN by splenocytes, indicates that lymphocytes possess a biologically relevant sigma receptor.

Affinity Labels↗
PubMed1992

Immunoregulatory properties of (+)-pentazocine and sigma ligands.

(+)-Pentazocine, phencyclidine, and other sigma ligands including 1,3-di-(o)-tolylguanidine (DTG), (+)-1-propyl-3-(3-hydroxyphenyl) piperidine [(+)-PPP] and haloperidol were investigated for their potential immunoregulatory properties. High concentrations (10(-5) M) of DTG and haloperidol were found to suppress in vitro murine splenocyte natural killer activity while equivalent concentrations of (+)-pentazocine, (-)-pentazocine and (+)-PPP were without effect. In a reciprocal fashion, lower doses (10(-9) M) of DTG enhanced natural killer activity. Sigma ligands were also found to affect in vitro polyclonal immunoglobulin production following mitogen stimulation. Specifically, high concentrations (10(-6) M) of haloperidol significantly (P < 0.001) suppressed pokeweed mitogen (PWM)-stimulated IgG and IgM production, yet enhanced lipopolysaccharide (LPS)-stimulated IgM production by murine splenocytes. Lower concentrations (10(-8) to 10(-10) M) enhanced (two- to fourfold) PWM-induced IgM production and LPS-stimulated IgG and IgM production. At high concentrations (10(-6)), (+)-pentazocine suppressed (P < 0.01) LPS-induced polyclonal IgG and IgM but enhanced (P < 0.01) PWM-induced IgM production. Both DTG and (-)-pentazocine (10(-8) to 10(-10) M) significantly augmented (two- to threefold) LPS-stimulated murine splenocyte production of polyclonal IgM. Intracellularly, (-)-pentazocine (10(-9) M), haloperidol (10(-7) M), DTG (10(-7) M) and (+)-PPP (10(-5) to 10(-9) M) enhanced forskolin (10(-6) M)-induced cAMP production in splenic lymphocytes while (+)-pentazocine was without effect. Collectively, the data suggest functional and biologically relevant sigma receptors on cells of the immune system.

Animals↗
PubMed1991

Repression of the human glycoprotein hormone alpha-subunit gene by glucocorticoids: evidence for receptor interactions with limiting transcriptional activators.

Expression of the glycoprotein hormone alpha gene is regulated divergently by glucocorticoids in different cell types. Coexpression of the glucocorticoid receptor (GR) with an alpha-CAT reporter gene caused activation of alpha promoter activity in fibroblasts, but repression in JEG-3 choriocarcinoma cells, indicating that cell-specific factors dictate positive vs. negative regulation of this promoter by GR. Cell-specific sequences and other enhancer elements in the the alpha gene have been relatively well characterized in JEG-3 cells, and this model was used to further examine the mechanism of transcriptional repression by glucocorticoids. Promoter mutagenesis indicated that the degree of GR-mediated repression was impaired by a variety of deletional and site-directed mutations between -171 and -111 bp, a region that includes both cell-specific and cAMP response elements (CREs). In an attempt to further localize a negative glucocorticoid response element (GRE) sequence, binding studies were used to assess GR interactions with alpha promoter DNA sequences. Using avidin-biotin complex DNA binding assays, a series of overlapping alpha promoter DNA sequences between -170 to 29 basepairs were tested, but each failed to bind GR, whereas a control GRE avidly bound receptor. Similarly, in competition assays in transfected CV-1 cells, the alpha gene 5'-flanking sequence did not compete for GR stimulation of a glucocorticoid responsive reporter gene, whereas a sequence that contains known GR-binding sites (murine mammary tumor virus) effectively inhibited GR-mediated expression. The absence of high affinity GR-binding sites in the alpha promoter suggested that mutations that affected GR inhibition may have eliminated recognition sites for transactivators, which are themselves targets for the GR, rather than altering specific negative GRE sites in the DNA sequence. To examine this possibility, GR repression was studied using chimeric transcription factors. The transcription-activating domains of several different proteins (CREB, thyroid hormone receptor, or VP16) were linked to the DNA-binding domain of Gal-4, and transcription was driven by the Gal-4 recognition site (UAS). GR markedly repressed transactivation by Gal-4-CREB and, to a lesser degree, the Gal-4-thyroid hormone receptor and Gal-4-VP16 chimeric proteins. Repression occurred when UAS was linked to either the alpha promoter or to the E1B promoter. Thus, inhibition occurs in the absence of either the CRE or the proximal alpha promoter. These results support a mechanism in which GR-mediated repression in JEG-3 cells occurs by receptor interference with the transactivating potential of enhancer-binding proteins or associated transcription factors.

Base Sequence↗
PubMed1989

Rapid analytical technique for the assessment of cell metabolic activity in marine microalgae.

A standard method for the assessment of cell viability has been developed for marine phytoplankton using an inexpensive stain, fluorescein diacetate (FDA), at .75 microM for 10 min. A flow cytometer was used as the fluorescence detector, providing an assessment of viability for each individual particle. Cell size and chlorophyll fluorescence per cell were assessed simultaneously, permitting an assignment of viability to specific subpopulations, thus increasing the power of the technique. A reasonable correspondence between FDA mean fluorescence intensity per cell and an independent metabolic indicator, photosynthetic capacity measured by 14C, was found. Both FDA mean fluorescence intensity and photosynthetic capacity vary as a function of cell volume. Recovery after extended periods of darkness indicate that cells that are FDA negative may not be dead, but merely quiescent or inactive.

Eukaryota↗
PubMed1988

Needle catheter jejunostomy: an unappreciated and misunderstood advance in the care of patients after major abdominal operations.

We evaluated the use of a needle catheter jejunostomy in 83 consecutive patients who underwent complicated abdominal operations. We used the needle catheter jejunostomy to deliver immediate postoperative nutrition (mean, 1,700 kcal/day) in 66 patients for a range of 4 to 80 days. In addition, the needle catheter jejunostomy was used to provide all maintenance fluid and electrolyte needs and to administer almost all required medications. No serious complications were related to use of the needle catheter jejunostomy, although easily controlled diarrhea occurred in 16 patients (19%). We concluded that the needle catheter jejunostomy is a safe and cost-effective means of delivering postoperative nutrition, fluid and electrolytes, and most medications in selected patients undergoing high-risk abdominal operations.

Adult↗
PubMedDate not supplied

Fibre mapping--a case study.

Fibre mapping, more commonly known as one-to-one taping, was developed in Germany approximately twenty years ago. The technique facilitates the distribution of fibres on a surface to be recorded. The impact of this technique on the investigation of serious crime has been reported in the European Fibre Group on several occasions. This paper represents a case study of the application of the technique. It is believed to be the first time that this technique has been successfully applied in the United Kingdom.

Journal Article↗