Detection of "lost" plasmids from Escherichia coli using excess ampicillin.
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Ampicillin Resistance↗
Biomedical subjects
A D Wright
Publications and source records attributed to A D Wright.
Soluble tumor necrosis factor receptors are present in human vitreous and shed by retinal pigment epithelial cells.
Tumor necrosis factor-alpha (TNF) has been implicated in the pathogenesis of several retinal diseases. Soluble forms of the TNF receptors, p55 (55 kDa) and p75 (75 kDa), have recently been identified in biological fluids and may regulate TNF activity. The potential biological significance of these receptors for the human retina was examined by determining their presence in human vitreous and their release from eye cup explants in which the retina has been removed leaving an intact retinal pigment epithelium (HRPE). Normal human vitreous and conditioned medium from eye-cup HRPE explants demonstrated the presence of soluble p55 and p75. Soluble p55 was significantly more abundant than p75 in all vitreous samples (P < 0.03). Conditioned medium from eye-cup HRPE explants contained significantly more soluble p55 than p75 (P < 0.00002). Enzyme-linked immunosorbent assay showed the presence of soluble p55, and not p75, in conditioned medium from primary cultured HRPE cells. Activation of the protein kinase C pathway in these cells with the phorbol ester PMA significantly increased the release of soluble p55 (P < or = 0.001); whereas, pharmacological inhibition of protein kinase C with calphostin-C significantly decreased the shedding of p55 (P < or = 0.001). The results indicate that primary cultured HRPE cells shed p55 and regulate this shedding in part through the protein kinase C pathway. The presence of soluble TNF receptors within normal human vitreous and within conditioned medium from the eye-cup HRPE explant model suggests that these soluble receptors may have a biological function in the eye.
Aged↗
Antimalarial activity: the search for marine-derived natural products with selective antimalarial activity.
In this short review, an approach to the isolation of potential antimalarial agents and lead compounds is outlined. A discussion of organism collection, followed by a description of biological testing and isolation methodologies, is also given. For two organisms, details of their secondary metabolite chemistry are reported. From one of these, Laurencia papillosa, the two aromatic compounds p-hydroxybenzaldehyde (1) and p-methoxybenzyl alcohol (2) were isolated. From the other, the tropical marine sponge Cymbastela hooperi, 15 diterpenes (3-17), which contain isonitrile, isothiocyanate, and isocyanate functionalities, are reported. Together with the diterpenes, three sesquiterpene hydrocarbons, 18-20, and the thiol, 21, were obtained. All structures were established by spectroscopic methods, particularly 1H-1H and 1H-13C shift-correlated 2D NMR spectroscopy and accurate mass measurement (HREIMS). The majority of isolates demonstrate significant and selective in vitro antimalarial activity. For compounds 4-17 a brief description of their possible structure-activity relationships is provided.
Animals↗
Hormone replacement therapy and diabetes mellitus.
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Aged↗
Marine natural products research: current directions and future potential.
Natural products research is increasingly turning to marine animals, plants, and microbes as source organisms. Several marine natural products are currently in preclinical and clinical evaluation, others show promising biological activities in in vitro and in vivo assays. Investigations of biological and chemical ecological phenomena in the marine world will contribute to a better understanding of marine habitats, and also provide a more founded basis regarding the search for pharmaceutically useful marine natural products.
Animals↗
Characterization of a chromosomally encoded 2,4-dichlorophenoxyacetic acid/alpha-ketoglutarate dioxygenase from Burkholderia sp. strain RASC.
The findings of previous studies indicate that the genes required for metabolism of the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) are typically encoded on broad-host-range plasmids. However, characterization of plasmid-cured strains of Burkholderia sp. strain RASC, as well as mutants obtained by transposon mutagenesis, suggested that the 2,4-D catabolic genes were located on the chromosome of this strain. Mutants of Burkholderia strain RASC unable to degrade 2,4-D (2,4-D- strains) were obtained by insertional inactivation with Tn5. One such mutant (d1) was shown to have Tn5 inserted in tfdARASC, which encodes 2,4-D/alpha-ketoglutarate dioxygenase. This is the first reported example of a chromosomally encoded tfdA. The tfdARASC gene was cloned from a library of wild-type Burkholderia strain RASC DNA and shown to express 2,4-D/alpha-ketoglutarate dioxygenase activity in Escherichia coli. The DNA sequence of the gene was determined and shown to be similar, although not identical, to those of isofunctional genes from other bacteria. Moreover, the gene product (TfdARASC) was purified and shown to be similar in molecular weight, amino-terminal sequence, and reaction mechanism to the canonical TfdA of Alcaligenes eutrophus JMP134. The data presented here indicate that tfdA genes can be found on the chromosome of some bacterial species and suggest that these catabolic genes are rather mobile and may be transferred by means other than conjugation.
2,4-Dichlorophenoxyacetic Acid↗
Induction of intercellular adhesion molecule-1 by tumor necrosis factor-alpha through the 55-kDa receptor is dependent on protein kinase C in human retinal pigment epithelial cells.
PURPOSE: To determine second messenger signaling pathways associated with tumor necrosis factor-alpha (TNF)-mediated induction of intercellular adhesion molecule (ICAM)-1 expression on human retinal pigment epithelial (HRPE) cells, a cell type known to express only the 55-kDa TNF receptor (TNFR p55). METHODS: SV 40-immortalized HRPE (SVRPE) cells were exposed to TNF with and without pretreatment with the protein kinase C (PKC) inhibitor calphostin C or the protein kinase A (PKA) inhibitor H8. SV40-immortalized HRPE cells also were treated with the PKC activator phorbol 12-myristate 13-acetate (PMA) or with the PKA activators forskolin plus 3-isobutyl-1-methyl-xanthine or dibutyryl cyclic adenosine monophosphate (cAMP) alone. Membrane fractions from untreated and treated SVRPE cells were assayed for PKC activity, and whole cell lysates were assayed for cAMP accumulation and PKA activity. Flow cytometry was performed on SVRPE cells using a monoclonal antibody specific to ICAM-1. RESULTS: Activation of TNFR p55 on SVRPE cells with TNF resulted in a rapid increase of PKC activity at 1 minute, with a subsequent downregulation to baseline. There was no increase in intracellular cAMP accumulation or PKA activity within the first 10 minutes; however, both increased within 30 minutes and returned to baseline within 1 hour. SV40-immortalized HRPE cells treated with TNF for 1 hour showed maximal induction of ICAM-1 expression at 18 hours. ICAM-1 induction by TNF treatment was inhibited by calphostin C pretreatment and not by H8 pretreatment. Protein kinase C activation with PMA for 3 hours was sufficient to induce ICAM-1 on SVRPE cells at 18 hours, whereas treatment with the PKA activators forskolin or dibutyryl cAMP did not induce ICAM-1 expression. CONCLUSIONS: Tumor necrosis factor sequentially activates the PKC and PKA pathways in SVRPE cells by way of the TNFR p55. The PKC pathway in necessary for TNF-mediated ICAM-1 upregulation, and specific activation of the PKC pathway with PMA is sufficient to induce ICAM-1 on these cells. SV40-immortalized HRPE cells may serve as a model in which to study further the functional signaling pathways associated with TNFR p55.
1-Methyl-3-isobutylxanthine↗
Hearing loss prevalence and risk factors among Sierra Leonean children.
OBJECTIVES: To determine hearing loss prevalence among a group of Third World children, to describe the physical examination and audiometric findings in the hearing-impaired children, and to assess the association of hearing loss with several known risk factors. It was hypothesized that chronic otorrhea would be the risk factor most strongly associated with hearing loss. DESIGN: Community screening program to identify and evaluate hearing-impaired children. Case-control analysis of hearing loss risk factors. A survey taker, blinded to the children's hearing status, ascertained risk factors. SETTING: Rural community in eastern province of Sierra Leone, West Africa. PATIENTS: Population-based sample of 2015 children aged 5 to 15 years. Risk factor analysis was performed in 184 children and an equal number of matched controls. MAIN OUTCOME MEASURE: Hearing loss determined according to World Health Organization, Geneva, Switzerland, definition. RESULTS: A total of 184 (9.1%) of 2015 children were found to have mild or greater hearing loss. The prevalence of bilateral profound hearing impairment was 4.0 per 1000. We assessed physical examination and audiometric findings. The risk factor most strongly associated with hearing loss was a history of otorrhea persisting longer than 1 month (odds ratio, 23.3; 95% confidence limits, 12.11, 45.40). CONCLUSIONS: A high prevalence of hearing loss was identified. Much of this impairment may result from chronic untreated or unrecognized ear infections. Further community-based studies of hearing-impaired children are necessary for planning preventive and curative programs.
Adolescent↗
Antibacterial triterpenoids from Dillenia papuana and their structure-activity relationships.
Two new oleanene-type triterpenoids, dillenic acids D and E, have been isolated from the leaves and stems of Dillenia papuana together with the new natural product 3-oxoolean-12-en-30-oic acid. Together with these compounds, the known compound, betulinic acid (3 beta-hydroxy-20(29)-lupen-28-oic acid) was isolated as the major component of the fractions studied. Dillenic acids D and E were characterized as 2,3-seco-2-oxoolean-12-en-3-methylester-30-oic acid and 1 alpha,3 beta-dihydroxyolean-12-en-30-oic acid and their nuclear magnetic resonance data were unambiguously assigned using two-dimensional nuclear magnetic resonance techniques. A comparison of antibacterial activities of these compounds with the earlier reported dillenic acids A-C indicated that, aside from a double bond in gamma- or delta-position to a carboxylic group, a ketone function in ring A of an oleanene-skeleton may be required for the observed activity.
Anti-Bacterial Agents↗
Intracranial pressure at high altitude and acute mountain sickness.
1. Raised intracranial pressure has been noted in severe forms of acute mountain sickness and high-altitude cerebral oedema, but the role of intracranial pressure in the pathogenesis of mild to moderate acute mountain sickness is unknown. 2. Serial measurements of intracranial pressure were made indirectly by assessing changes in tympanic membrane displacement in 24 healthy subjects on rapid ascent to 5200 m. 3. Acute hypoxia at 3440 m was associated with a rise in intracranial pressure, but no difference was found in pressure changes at 4120 or 5200 m in subjects with or without symptoms of acute mountain sickness. 4. Raised intracranial pressure, though temporarily associated with acute hypoxia, is not a feature of acute mountain sickness with mild or moderate symptoms.
Acute Disease↗
Biological activities of cyanobacteria: evaluation of extracts and pure compounds.
A total of 80 lipophilic and hydrophilic extracts obtained from 20 samples of cultured freshwater and terrestrial cyanobacteria were investigated for their biological activities. Of all the extracts, 26% exhibited a significant lethal effect against brine shrimp. Out of 54 extracts tested for antimicrobial activity, 78% showed antibacterial and 45% antifungal activities. Of 30 extracts tested for cytotoxicity against KB cells, none was found to be active. Bioassay-guided fractionation of the lipophilic extracts of Fischerella ambigua led to the isolation of three compounds; ambigols A (1) and B (2), and tjipanazole D (3). Compounds 1 and 2 exhibited antibacterial, antifungal, cytotoxic, molluscicidal, and anti-inflammatory, and antiviral activities. Tjipanazole D (3) showed moderate antibacterial properties.
Animals↗
Phylogeny of the fish parasite Ichthyophthirius and its relatives Ophryoglena and Tetrahymena (Ciliophora, Hymenostomatia) inferred from 18S ribosomal RNA sequences.
Phylogenetic relationships within the subclass Hymenostomatia were inferred from the comparisons of three new SSrRNA gene sequences from Ichthyophthirius multifiliis (1,751 bp), Ophryoglena catenula (1,748 bp), and Tetrahymena corlissi (1,753 bp). Using maximum-parsimony and distance-matrix methods, Ichthyophthirius and Ophryoglena were consistently paired and formed a sister group to the tetrahymenines, consistent with their placement in the Ophryoglenina. Tetrahymenids formed a monophyletic group that was divided into main lineages: T. corlissi diverged from the base of the lineage that included T. thermophila.
Animals↗
Diabetes care in South Asian and white European patients with type 2 diabetes.
Aspects of diabetes care in South Asian and white European patients with Type 2 diabetes attending a hospital review clinic were explored. Among the clinic population of 1710 patients, 258 (15%) were of South Asian origin. A significantly greater proportion (95% CI for difference in proportions 8-22%) of these patients was treated with oral hypoglycaemic drugs than in white Europeans, in whom there was a correspondingly greater proportion receiving insulin treatment. In a case-control study, where 154 patients in each racial group were stratified according to treatment regimen, significantly more South Asian patients (13/30 vs 6/30, p < 0.05) on insulin were treated with a once-daily regimen. Despite these observed differences in treatment of diabetes, glycaemic control was no worse in South Asian patients when compared to their white European counterparts. South Asian diabetic patients attending hospital diabetes clinics in the UK can experience similar levels of glycaemic control to white Europeans.
Asia↗
Exogenous tat protein activates central nervous system-derived endothelial cells.
Tat protein, an HIV gene product known to be secreted extracellularly, was tested to determine its role in the dissemination of HIV into the central nervous system (CNS). Tat was shown to activate human CNS-derived endothelial cells (CNS-EC) by the increase in the expression of E-selectin, the synthesis of IL-6, and the secretion of plasminogen activator inhibitor-1 (PAI-1). Tat also functioned synergistically with tumor necrosis factor alpha (TNF). AIDS brains stained for tat in situ, demonstrated positive cells. These data suggest that secreted tat protein may increase leukocyte binding, and alter the blood-brain barrier permeability to enhance dissemination of HIV-infected cells into the CNS.
Acquired Immunodeficiency Syndrome↗
Cytotoxic and antibacterial dihydrochalcones from Piper aduncum.
Bioactivity-guided fractionation of a CH2Cl2 extract from the leaves of Piper aduncum afforded three new dihydrochalcones, piperaduncins A [3], B [4], and C [5], as well as two known dihydrochalcones, 2',6'-dihydroxy-4'-methoxydihydrochalcone [1] and 2',6',4-trihydroxy-4'-methoxydihydrochalcone [2] (asebogenin), together with sakuranetin, anodendroic acid methyl ester, and the carotenoid lutein. The structures of the isolates were elucidated by spectroscopic methods, mainly 1D- and 2D nmr spectroscopy. The proposed stereochemistry for compound 4 was deduced by NOESY spectroscopy and the corresponding energy minimum was established by molecular modelling calculations and translated into a 3D structure.
Animals↗
Inerminosides A and B, two novel complex iridoid glycosides from Clerodendrum inerme.
The leaves of Clerodendrum inerme have yielded two new iridoid biglycosides which have been characterized as 2'-O-[5"-O-(8-hydroxy-2,6-dimethyl-2(E)-octenoyl)-beta-D-apiofuranosy l]- mussaenosidic acid (inerminoside A) [1], and 2'-O-[5"-O-(8-hydroxy-2,6-dimethyl-2(E),6(E)-octadienoyl)-beta-D- apiofuranosyl]-8-epi-loganic acid (inerminoside B [2]), respectively. Structure elucidation was carried out both chemically and spectroscopically.
Africa↗
Antibacterial triterpenoid acids from Dillenia papuana.
Three new oleanene-type triterpenoids, dillenic acids A [1], B [2], and C [3], and two known compounds, 3-oxoolean-1,12-dien-30-oic acid [4] (a new natural product) and the lupene derivative betulinaldehyde, have been isolated from the Papua New Guinean medicinal plant Dillenia papuana. The structures of the new compounds were elucidated as 2 alpha-hydroxy-3-oxoolean-12-en-30-oic acid, 2-oxo-3 beta-hydroxyolean-12-en-30-oic acid and 1 alpha-hydroxy-3-oxoolean-12-en-30-oic acid. The 1H- and 13C-nmr data of all new compounds were assigned unambiguously using a variety of 2D nmr experiments including 1H-1H-COSY, HMQC, HMBC, and NOESY experiments. Of these compounds, 1-4 showed antibacterial activities against Bacillus subtilis, Escherichia coli, and Micrococcus luteus.
Anti-Bacterial Agents↗
Biological activities of selected marine natural products.
Sixty-nine natural products derived from Phaeophyta (brown algae), Rhodophyta (red algae), Porifera (sponges), Cnidaria (soft corals), and Mollusca (nudibranchs) were investigated for their cytotoxic, antimalarial, and antimicrobial effects. Fifty-six were found to mediate a positive response in one or more of these test systems.
Animals↗