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Biomedical subjects

A L Bailey

Publications and source records attributed to A L Bailey.

At least 19 recordsLinked to original sources
PubMed2006

Transient loss of terminals from non-peptidergic nociceptive fibers in the substantia gelatinosa of spinal cord following chronic constriction injury of the sciatic nerve.

It is well known that following peripheral nerve injury, there are numerous changes in neurotransmitter and neuropeptide expression in the superficial dorsal horn, the dorsal root ganglion and the periphery. Of particular interest are the relative contributions of two sub-types of unmyelinated C-fibers in the initiation and maintenance of chronic pain, the peptidergic, and the non-peptidergic. Evidence gathered in recent years has led researchers to believe that the non-peptidergic nociceptive primary afferents are functionally distinct from their peptidergic counterpart. For our study, we used a well-established animal model of constriction neuropathy (the Kruger model) and studied Wistar rats at 5, 7, 10, 15 and 21 days after nerve lesion caused by the application of a fixed-diameter polyethylene cuff to the left sciatic nerve. Animals were assessed for the onset and evolution of mechanical allodynia using calibrated von Frey filaments and were additionally tested for thermal (heat and cold) hypersensitivity. Immunocytochemical detection of calcitonin gene-related peptide (CGRP) and isolectin B4 (IB4) binding was used to visualize the dorsal horn distribution of the boutons from the peptidergic and non-peptidergic fibers respectively. Using confocal microscopy and image analysis, we detected a significant decrease in the density of IB4-labeled boutons, ipsilateral to the lesion, at seven and 10 days following nerve injury. The density of IB4-labeled varicosities retuned to control levels by 15 days. There were no significant changes in the density of CGRP-labeled varicosities at all time points examined. Applying electron microscopy, we initially detected degenerative changes in the central elements of type I glomeruli and then a considerable reduction in their number followed by recovery at 15 days post-lesion. As the central boutons of type Ia represent varicosities from the fibers which bind IB4, the ultrastructural changes confirmed that there was a bona fide transient loss of varicosities, not simply a loss of IB4 binding. These data indicate that, in this animal model, morphological changes in the nociceptive C-fiber input of the rat dorsal horn are restricted to the non-peptidergic sub-population and are transient in nature. Furthermore, such changes do not correlate with the time-course of the allodynia.

Animals↗
PubMed2005

Postnatal development of ectopic sensory fibers containing endomorphin-2 in the white matter of the spinal cord of a transgenic mouse expressing nerve growth factor in oligodendrocytes.

Transgenic mice ectopically expressing nerve growth factor in oligodendrocytes have high levels of nerve growth factor immunoreactivity in the white matter of the spinal cord from birth until 2 months of age. The nerve growth factor over-expression leads to the appearance of ectopic substance P containing sensory fibers in the white matter of the spinal cord that persist throughout the life of the animal. These transgenic mice have been found to display hypersensitivity to a thermal stimulus following a sensitizing pinch stimulus known to release endogenous substance P. Surprisingly, this hypersensitivity is completely reversed following the administration of morphine, to the extent that transgenic mice become less sensitive to pain than the wild type mice given morphine. Endomorphin-2, an endogenous opioid peptide, has been found co-localized with substance P in primary sensory fibers in the spinal cord. In this study, we show that the ectopic fibers also express endomorphin-2, and describe the postnatal development of such expression, as detected by immunocytochemistry. We confirmed that endomorphin-2 expression starts later in the postnatal period than substance P. Surprisingly, transgenic animals had delayed appearance of endomorphin-2 in the superficial dorsal horn, compared with wild type, and expressed particularly high levels of endomorphin-2 immunoreactivity in the ectopic fibers from postnatal days 10-30, coinciding with the peak of nerve growth factor expression in oligodendrocytes. Endomorphin-2 immunoreactivity was still readily detected in ectopic fibers of 120-day-old animals. Furthermore, we detected immunoreactivity for the mu-opioid receptor in the ectopic fibers, where it was co-localized with endomorphin-2 immunoreactivity. In the superficial dorsal horn, there were no apparent differences in the distribution and intensity of mu-opioid receptor immunoreactivity between wild type and transgenic animals. Taken together, these data could provide an explanation for the enhanced effect of opioid analgesics in transgenic mice, when compared with control mice, as well as provide the basis for studies of the postnatal development of the hyperalgesia and allodynia demonstrated by these animals.

Animals↗
PubMed2001

Indexical and symbolic referencing: what role do they play in children's success on theory of mind tasks?

Numerous measures have been employed in the last 17 years to assess theory of mind (ToM). The literature reports marked variability in the age at which children succeed on these measures. To account for this variability, researchers have provided explanations ranging from cognitive shifts and voids to the inability to understand the language of the tasks or to social/pragmatic considerations, all of which tell us little if anything about the internal mechanism underlying ToM. The main purpose of this paper is to provide a comprehensive theoretical account of children's success and the discrepancies found across different ToM tasks. We test the hypothesis that children's understanding of ToM is sensitive to the basic elements of language, that is, to whether the language is indexical or symbolic. Support for this account was found in the analysis of selected test protocols in four published studies of ToM, and new data collected from 53 children (4--6 years) which showed that a higher percentage of children succeeded on tasks with a high ratio of indexical to symbolic references than on tasks with a high ratio of symbolic to indexical references. There was also a main effect of age with older children succeeding at higher rates on both tasks than younger children. Our findings suggest that indexical representation can afford ToM understanding in 4-year-olds, but is not sufficient for a more mature ToM. The latter requires symbolic representation that was demonstrated by the majority of 5--6-year-olds.

Child↗
PubMed2000

Efficient encapsulation of DNA plasmids in small neutral liposomes induced by ethanol and calcium.

Efficient encapsulation of DNA plasmids inside small, neutral liposomes composed of 1,2-dioleoyl-sn-phosphatidylcholine (DOPC), DOPC/DOPE (1,2-dioleoyl-sn-phosphatidylethanolamine) (1:1) and DOPC/DOPE/cholesterol (1:1:1) was achieved by the addition of ethanol and calcium chloride to an aqueous mixture of small unilamellar vesicles (SUVs) and plasmid. Following dialysis against low-salt buffer, the neutral lipid complexes (NLCs) had average effective diameters less than 200 nm and encapsulated up to 80% of the DNA. Optimum Ca(2+) and ethanol concentrations for each lipid mixture were determined by statistically designed experiments and mathematical modeling of trapping efficiency. NLCs are unilamellar, have neutral surface potentials, and retain entrapped DNA at pH 4.0 and in serum at 37 degrees C. The circulation and clearance properties of the complexes following intravenous administration in mice are similar to empty neutral liposomes, and the toxicity of NLCs are expected to be significantly reduced compared to other non-viral gene-delivery systems. The NLC encapsulation method, if it can be combined with effective targeting and endosome-release technologies to achieve efficient and tissue-specific transfection, may represent an important alternative to current systemic gene therapy approaches.

Animals↗
PubMed2000

Enzymatic mutation detection (EMD) of novel mutations (R565X and R1523X) in the FBN1 gene of patients with Marfan syndrome using T4 endonuclease VII.

The Enzymatic Mutation Detection (EMDtrade mark) method is a streamlined and improved version of the original Enzymatic Cleavage of Mismatch (EMC) method. EMD is a fully homogeneous, rapid four step procedure that allows for detection and localization of mismatched or unmatched nucleotides within heteroduplex DNA. To test the utility of EMD for use in the screening of large and complex genes, the fibrillin 1 (FBN1) gene was scanned in a cohort of six patients diagnosed with connective tissue disorders. Four of the six patients were diagnosed with classic Marfan syndrome (MFS). The results were compared with a previous MDEtrade mark scanning of the same patient cohort. Two causative mutations, R565X and R1523X, were detected by EMD that were not detected by MDE. In both cases, the mutation resulted in premature termination of translation. In addition, several polymorphisms were detected by the enzymatic approach that failed detection by heteroduplex analysis. We propose that the EMD method is a sensitive and rapid approach to mutation detection in large genes such as FBN1.

Adult↗
PubMed2000

Effects of lycopene and lutein supplementation on the expression of functionally associated surface molecules on blood monocytes from healthy male nonsmokers.

It has been suggested that dietary carotenoids can enhance immune function. Supplementation with beta-carotene (15 mg daily) was previously shown to enhance human monocyte function. To examine the effect of other dietary carotenoids, two similar independent studies were done. Healthy adult male nonsmokers were randomly assigned to receive lycopene (study 1), lutein (study 2), or placebo for 26 days, followed by the alternative treatment for another 26 days. The expression of functionally related monocyte surface molecules was quantified by laser flow cytometry before and after each treatment period. There was a significant increase in plasma levels of each carotenoid following dietary supplementation, but the effects on monocyte surface molecule expression were not as striking as those observed after beta-carotene supplementation. These findings emphasize that it cannot be assumed that the effect of one carotenoid will be the same as another, even at the same level of intake.

Adolescent↗
PubMed1999

Beta-carotene and lycopene, but not lutein, supplementation changes the plasma fatty acid profile of healthy male non-smokers.

Polyunsaturated fatty acids (PUFAs) are highly susceptible to free radical attack. In vitro studies of carotenoids--including beta-carotene, lycopene, and lutein--have shown them to be effective quenchers of singlet oxygen, to have good radical-trapping properties, or to be effective peroxyl radical scavengers (or to have a combination of these qualities). If carotenoids act as antioxidants in vivo, then arguably, plasma PUFA should be conserved. The objective of the current study was to answer the question "Does supplementation with beta-carotene, lycopene, or lutein, at dietarily achievable levels, over a time period known to significantly increase circulating carote concentrations, lead to an observable increase in fasting plasma PUFA?" The normal diets of human volunteers were supplemented with either 15 mg/day beta-carotene (n = 25), lycopene (n = 23), or lutein (n = 21) for 26 days in three independent double-blind, placebo-controlled supplementation studies. Supplementation with beta-carotene increased plasma linoleic acid but left the polyunsaturated:saturated (P:S) fatty acid ratio unaltered. In contrast, supplementation with lycopene reduced linoleic acid, which resulted in a large decrease in the P:S ratio. Lutein supplementation had no effect. It was concluded that neither beta-carotene, lycopene, nor lutein supplementation engender antioxidant effects that lead to the widespread general conservation of plasma PUFAs. Beta-carotene and lycopene supplementation appear to interact with the metabolism of linoleic acid, the "essential" fatty acid, resulting in either an increase (beta-carotene) or decrease (lycopene) in its plasma concentration. Alterations in plasma 18:2 or P:S ratios could ultimately lead to changes in tissue cellular membrane composition and hence to alterations in membrane fluidity and cell-surface protein expression.

Adolescent↗
PubMed1999

High performance liquid chromatography method for the determination of pyridoxal-5-phosphate in human plasma: how appropriate are cut-off values for vitamin B6 deficiency?

OBJECTIVES: Application of a HPLC (high performance liquid chromatography) method, using cyanide derivatisation, to the determination of plasma pyridoxal-5-phosphate (PLP) concentrations as an indicator of vitamin B6 adequacy. SETTING: The study was performed at the Institute of Food Research, Norwich, UK. Blood samples were taken at the Institute, at Health Centres, or in the volunteer's home. SUBJECTS: 51 adolescent, 131 adult, 68 non-institutionalized elderly and 44 aged (>73 y) volunteers were recruited from local authority schools, local Health Centres and General Practitioners. RESULTS: The mean PLP recovery was 92.8%. The intra- and inter-assay coefficients of variation were 2.8% and 5.2% respectively. Mean PLP concentrations for males and females, respectively, were: adolescents (13-14 y), 36.4 and 43.5 nM; adults (20-64 y), 39.2 and 40.0 nM; elderly (68-73 y), 34.8 and 35.3 nM; aged (>73 y), 57.8 and 49.0 nM. Percentages of subjects with PLP concentrations <34.4 nM were over 26% in all population groups. Mean vitamin B6 intakes (microg/g protein intake), as assessed by weighed dietary records, were all above reference nutrient intakes (15 microg/g protein). CONCLUSIONS: An HPLC method, using cyanide derivitisation, has been applied to the determination of plasma PLP. Comparisons of results for local population groups with current cut-off values for plasma PLP, show large numbers of volunteers at risk of vitamin B6 deficiency although this is not reflected by vitamin B6 intakes calculated from food tables. The 34.4 nM cut-off value for value for plasma PLP, indicating deficiency, is questioned.

Adolescent↗
PubMed1998

Determination of total long-chain fatty acids in human plasma and lipoproteins, before and during copper-stimulated oxidation, by high-performance liquid chromatography.

An improved method for the high-performance liquid chromatographic determination (HPLC) of total or free long-chain (> C12) fatty acids in small volumes (10 microL) of human plasma and lipoprotein samples is described. The method is based on the formation of 2-nitrophenyl-hydrazine (2-NPH) derivatives and offers an alternative to gas chromatographic (GC) fatty acid determination. The retention of 2-NPH fatty acid derivatives on the HPLC system differs from the typical pattern produced by GC separation, thus offering a powerful tool for confirmation of peak identification where GC peak resolution is poor. Fatty acids determined include saturates [myristic acid, C14:0; palmitic acid, C16:0; stearic acid, C18:0; eicosanoic acid, C20:0; docosanoic acid, C22:0; and tetracosanoic acid, C24:0], monounsaturates [palmitoleic, C16:1; petroselenic, C18:1n12; oleic, C18:1n9; and erucic, C22:1], and polyunsaturates [linoleic, C18:2; linolenic, C18:3n3; gamma-linolenic acid, C18:3n6; eicosatrienoic, C20:3; arachidonic, C20:4; eicosapentanoic, C20:5; docosahexanoic, C20:6; and docosatetraenoic, C22:4]. Mean recoveries of fatty acids added to LDL samples were 94.1-109.4%, and intraassay coefficients of variation for the major fatty acids in human plasma were 2.7-6.9%. The potential of the method for further development is discussed. Long-chain fatty acid profiles are given for plasma and very low-, low, and high-density lipoprotein (before and during copper-stimulated oxidation) from human blood.

Chromatography, High Pressure Liquid↗
PubMed1998

Automated fluorescent analysis procedure for enzymatic mutation detection.

The Enzymatic Mutation Detection (EMD) assay detects mutations or polymorphisms in DNA. The assay procedure takes <1 h and is followed by electrophoretic detection. We report an automated procedure, using fluorescently labeled probe and quantitative analysis on the ABI Prism 377 DNA Sequencer, that improves on earlier methods (1, 2) by eliminating the need for sample purification, shortening the hybridization time, and increasing the signal-to-noise ratio. The EMD assay uses the bacteriophage resolvase T4 endonuclease VII, which cleaves the heteroduplex molecules at the mismatch site, forming two shorter fragments that are resolved by gel electrophoresis. Unlike existing mutation techniques, the EMD method uses a single protocol to identify point mutations, deletions, and insertions for all DNA fragments. Test DNA samples are assayed directly from PCR reactions, and fragments up to 4 kb in size have been assayed successfully. A independent analysis on the p53 tumor suppressor gene from clinical samples has shown 100% sensitivity and 94% specificity. Because the fluorescent EMD assay has been optimized for high signal-to-noise ratios, mutations can be identified in mixed samples containing up to a 20-fold excess of normal DNA.

Animals↗
PubMed1997

pH-induced destabilization of lipid bilayers by a lipopeptide derived from influenza hemagglutinin.

A synthetic twenty-one amino acid peptide (AcE4K) based on the amino acid sequence of the influenza HA2 fusion peptide was coupled to a distearoylglycerol lipid anchor by amidation of an N-terminal lysine side chain. The secondary structure of Lipo-AcE4K incorporated into POPC (1-palmitoyl-2-oleoyl-sn-phosphatidylcholine) liposomes was not measurably affected by pH, but increased membrane penetration was indicated by tryptophan fluorescence. At outer monolayer concentrations up to 10 mol%, Lipo-AcE4K formed stable liposomes with POPC and EPC/Chol (egg phosphatidylcholine/cholesterol) (55:45) at pH 7.5. Acid-induced destabilization and fusion of these vesicles were demonstrated by fluorescent lipid mixing and contents leakage assays, and by freeze-fracture electron microscopy. Membrane destabilization increased with increasing lipopeptide concentrations, decreasing pH, inclusion of cholesterol, and incorporation of lipopeptide into the inner monolayer as well as the outer monolayer of the liposomes. Fusion of liposomes bearing Lipo-AcE4K with erythrocyte ghosts was demonstrated by lipid mixing and fluorescence microscopy.

Amino Acid Sequence↗
PubMed1997

Membrane fusion with cationic liposomes: effects of target membrane lipid composition.

Determination of the mechanisms by which cationic liposomes adhere to and fuse with biological membranes is important to understanding how these lipid vesicles mediate cellular transfection. To determine what role the lipid composition of "target" membranes might have in promoting fusion with cationic liposomes, we have examined the ability of large unilamellar vesicles composed of 1,2-dioleoylsn-phosphatidylethanolamine (DOPE) and N,N-dimethyl-N,N-di-9-cis-octadecenylammonium chloride (DODAC) (1:1) to fuse with target liposomes of varying composition in the absence of DNA. Membrane fusion was promoted by increased negative surface charge and, for liquid crystalline lipids, by increased acyl chain unsaturation in target liposomes. However, the presence of disaturated phospholipids promoted fusion below the gel to liquid crystalline transition temperature, an effect which was eliminated by the addition of cholesterol. It was also shown that DOPE/DODAC (1:1) LUVs fused with erythrocyte ghosts and that this fusion was blocked by the presence of serum. Membrane fusion was determined by a quantitative fluorescent lipid mixing assay and qualitatively by freeze-fracture electron microscopy and fluorescence microscopy.

Animals↗
PubMed1997

The effect of beta-carotene supplementation on the immune function of blood monocytes from healthy male nonsmokers.

Although there is strong epidemiologic evidence that diets rich in carotenoids such as beta-carotene are associated with a reduced incidence of cancer, the cellular mechanisms underlying this phenomenon remain unknown. This article describes the effect of dietary beta-carotene supplementation on both the expression of functionally associated surface molecules on human monocytes and on the secretion of the cytokine tumor necrosis factor-alpha (TNF-alpha) by monocytes, all of which are involved in the initiation and regulation of immune responses involved in tumor surveillance. A double-blind, placebo-controlled, crossover study was undertaken in which 25 healthy, adult male nonsmokers were randomly assigned to receive beta-carotene (15 mg daily) or placebo for 26 days, followed by the alternative treatment for a further 26 days. The expression of functionally related monocyte surface molecules was quantified by flow cytometry, and ex vivo secretion of TNF-alpha was quantified by an enzyme-linked immunosorbent assay, before and after each treatment period. After dietary supplementation there were significant increases in plasma levels of beta-carotene and in the percentages of monocytes expressing the major histocompatibility complex class II molecule HLA-DR and the adhesion molecules intercellular adhesion molecule-1 and leukocyte function-associated antigen-3. In addition, the ex vivo TNF-alpha secretion by blood monocytes was significantly increased after supplementation. These findings suggest that moderate increases in the dietary intake of beta-carotene can enhance cell-mediated immune responses within a relatively short period of time, providing a potential mechanism for the anticarcinogenic properties attributed to beta-carotene.

Adult↗
PubMed1997

Measurement of aldehydes in low density lipoprotein by high performance liquid chromatography.

A modified procedure is presented for the HPLC determination of nanomolar concentrations of n-alkanals, hydroxyalkenals, malondialdehyde and furfural in biological fluid. The modifications allow aldehyde profile analysis of small samples of fresh, human, low density lipoprotein (LDL), enabling more detailed studies of LDL fatty acid peroxidation. Aldehydes are reacted with 1,3-cyclohexanedione to produce fluorescent derivatives which are separated by gradient, reversed phase, high performance liquid chromatography (HPLC). Analysis time has been reduced by shortening the sample preparation. Sensitivity has been increased by miniaturization of the derivatisation procedure, reducing required sample size. Recoveries of added aldehydes have been improved. In addition, the method presented allows determination of three further aldehydes, not measured previously by CHD methods: malondialdehyde, formaldehyde and furfural. Recovery and variability data and concentrations of aldehydes found in human LDL are given. The capacity of the method for further development, to enable determination of other aldehydes such as the trans, 2-alkenals, is also demonstrated.

Aldehydes↗
PubMed1997

Relationships between micronutrient intake and biochemical indicators of nutrient adequacy in a "free-living' elderly UK population.

Nutritional assessments are frequently based on amounts of nutrients consumed. In the present paper the usefulness of nutrient intake data for assessing nutrient adequacy is examined in an elderly British population. Subjects were "free-living' elderly aged 68-90 years (sixty men, eighty-five women) in Norwich. Forty-two of forty-nine surviving males and sixty-seven of seventy-nine surviving females were reassessed after 2 years. With few exceptions, estimated micronutrient intake was not statistically predictive of biochemical measures of nutrient adequacy. Initial biochemical measures of nutritional adequacy were compared with those found 2 years later in an attempt to assess whether initial biochemical assessment was predictive of the "longer term' situation. Biochemical measurements at the start of the study were correlated to the same measurements made 2 years later for: serum ferritin, haemoglobin and erythrocyte count, whole-blood Se-glutathione peroxidase (EC 1.11.1.9; males only), plasma Cu, alkaline phosphatase (EC 3.1.3.1), ascorbic acid, vitamin B6 (pyridoxal-5-phosphate), folate and vitamin B12, total erythrocyte thiamin (males only), riboflavin (erythrocyte glutathione reductase (EC 1.6.4.1) activation coefficient): but not for: erythrocyte Cu-superoxide dismutase (EC 1.15.1.1) or plasma Zn. Either only small changes, or no changes, in mean values were seen over the 2 years for most of the biochemical measures. One exception was a large increase in plasma folate. The only important "negative' features seen at 2-year follow up were a large fall in serum ferritin concentration and a large increase in the activity of two antioxidant defence enzymes, superoxide dismutase and glutathione peroxidase. As judged by currently accepted biochemical deficiency threshold values, a small proportion of subjects were possibly at risk of Fe (3% men; 1% women), folate (7%, 3%), thiamin (12%; 3%) and vitamin C (15%; 17%) deficiency. Many more appeared to be at risk of vitamin B6 (42%; 47%) and riboflavin (77%; 79%) deficiency. It was concluded that the requirements of the elderly for vitamins B1, B2 and C, and the biochemical deficiency threshold values used to indicate vitamin B6 deficiency, need review.

Aged↗