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Biomedical subjects

P Whiting

Publications and source records attributed to P Whiting.

At least 37 records · Page 2Linked to original sources

Ecdysteroids and bufadienolides from Helleborus torquatus (Ranunculaceae).

Three bufadienolides, hellebortin A (5-[beta-D-glucopyranosyloxy]-10,14,16-trihydroxy-19-nor-[5beta,10beta,14beta,16beta]-bufa-3,20,22-trienolide [1]), hellebortin B (5-[beta-D-glucopyranosyloxy]-3,4-epoxy-14-hydroxy-19-oxo-bufa-20,22-dienolide [2]) and hellebortin C (5-[beta-D-glucopyranosyloxy]-3,4-epoxy-10,14-dihydroxy-19-nor-bufa-20,22-dienolide [3]), together with 20-hydroxyecdysone 3-O-beta-D-glucoside (4) and 20-hydroxyecdysone (5) have been isolated by bioassay- and RIA-directed HPLC analyses of a methanol extract of the seeds of Helleborus torquatus. The structure and relative stereochemistry of the novel bufadienolide hellebortin A (1) and the structures of hellebortin B (2) and hellebortin C (3) were determined unambiguously by comprehensive analyses of their 1D and 2D NMR data. These five compounds are isolated from Hellborus torquatus for the first time. The biological activities of compound 1, 4 and 5 as ecdysteroid agonists and antagonists have been assessed.

Animals↗

Phytoecdysteroids in seeds of Lloydia serotina (Liliaceae).

Seeds of a number of species in the Liliaceae (sensu Brummitt, 1992) were examined for the presence of ecdysteroid agonist and antagonist activities. No species were antagonistic to 20-hydroxyecdysone action on the ecdysteroid-responsive Drosophila melanogaster B(II) cell line and only one extract, that of Lloydia serotina, was agonistic. This activity is attributable to the presence of phytoecdysteroids as detected by ecdysteroid-specific radioimmunoassay and the agonist version of the B(II) bioassay. HPLC in conjunction with radioimmunoassay and bioassay have been used to determine the ecdysteroid profile. The major ecdysteroids present are identified as 20-hydroxyecdysone and polypodine B (5beta,20-dihydroxyecdysone).

Journal Article↗

8-O-acetylharpagide is not an ecdysteroid agonist.

We have reinvestigated the activity of 8-O-acetylharpagide, an iridoid glucoside, as an ecdysteroid agonist. Elbrecht et al. (Insect Biochem. Mol. Biol. 26 (1996) 519) isolated a preparation of this compound from Ajuga reptans L. and ascribed ecdysteroid agonist activity on the basis of the induction of an ecdysteroid-like response in Drosophila melanogaster KcO cells, the displacement of [3H]ponasterone A from the Drosophila receptor and the activation of an ecdysteroid-regulated gene in a transactivation assay. We provide evidence that the agonist activity derives from contaminating ecdysteroids; A. reptans is a species rich in ecdysteroids. Purified 8-O-acetylharpagide is not active in the D. melanogaster B(II) cell bioassay, neither as an agonist nor as an antagonist, nor does it displace [3H]ponasterone A from dipteran or lepidopteran ecdysteroid receptor complexes.

Animals↗

Thy1 glomerulonephritis induced in young lewis rats accelerates age-related glomerulosclerosis.

Age-related and disease-induced glomerulosclerosis (GS) in rats have both been well defined in a number of strains and experimental models, but the inter-relationship between the two is not clear. The present study was undertaken to compare the pattern of glomerular injury in these two types of GS. One- and two-shot Thy1 glomerulonephritis (GN) was induced at 2 months of age and followed for 12 months. At 12 months histological injury in proteinuric rats was characterized by segmental hyaline lesions. Two-shot Thy1 GN resulted in accelerated, but morphologically identical injury at 8 months. Histological lesions predictive of subsequent accelerated GS were evaluated at 1, 2, 4 and 6 months. In this regard, glomerular hypercellularity, rather than hypertrophy or matrix increase, was the most consistent histological index of later accelerated disease. The profibrotic cytokines transforming growth factor (TGF)-beta(1) and -beta(3) were localized distinctly to segmental hyaline lesions, but not to areas of matrix increase within the glomerular tuft. This study reveals that GS after Thy1 GN represents acceleration of an age-related disease, presents evidence for use of prolonged glomerular hypercellularity as the best histological index of future disease progression, and correlates the key lesion of GS in these animals, the segmental hyaline lesion, with the presence of TGF-beta peptides.

Aging↗

Screening of environmental contaminants for ecdysteroid agonist and antagonist activity using the Drosophila melanogaster B(II) cell in vitro assay.

The B(II) bioassay was developed as a rapid and reliable tool for detecting potential insect growth regulators acting as ecdysteroid receptor (ant)agonists. Based on an ecdysteroid-responsive cell line from Drosophila melanogaster, this microplate assay is ideally suited to the evaluation of environmental contaminants as potential endocrine disrupters. Data are presented for about 80 potential environmental contaminants, including industrial chemicals, pesticides, pharmaceuticals, phytoestrogens, and vertebrate steroids, and are compared with data for known (ant)agonists. Apart from androst-4-ene-3,17-dione (a weak antagonist), vertebrate steroids were inactive at concentrations up to 10(-3) M. The vast majority of xenobiotics also showed no (ant)agonist activity. Among the industrial chemicals, antagonistic activity was observed for bisphenol A median effective concentration (EC50) of 1.0 x 10(-4) M and diethylphthalate (EC50 of 2.0 x 10(-3) M). Some organochlorine compounds also showed weak antagonistic activity, including o,p'-dichlorodiphenyldichloroethylene (DDE), p,p'-DDE, dieldrin, and lindane (EC50 of 3.0 x 10(-5) M). For lindane, bisphenol A, and diethylphthalate, activity is not associated with impurities in the samples and, for lindane and bisphenol A at least, the compounds are able to compete with ecdysteroids for the ligand binding site on the receptor complex, albeit at concentrations very much higher than those found in the environment. The only pharmaceutical showing any detectable antagonist activity was 17alpha-ethynylestradiol. In the context of recent publications on potential endocrine disruption in marine and freshwater arthropods, these findings suggest that, for some compounds (e.g., diethylstilbestrol), ecdysteroid receptor-mediated responses are unlikely to be involved in producing chronic effects. The B(II) assay has a potentially valuable role to play in distinguishing between endocrine-mediated, which normally occur at submicromolar concentrations, and pharmacological effects in insects and crustaceans.

Animals↗

A rapid and systematic review of the clinical effectiveness and cost-effectiveness of debriding agents in treating surgical wounds healing by secondary intention.

BACKGROUND: Most surgically sutured wounds heal without any complication. However, in some cases wound healing can be delayed due to the presence of infection or wound breakdown. This can result in the wounds becoming cavity wounds and thus necessitate healing by secondary intention. Other surgical wounds that are not sutured but left to heal by secondary intention include abscess cavities such as perianal abscesses or breast abscesses. Surgical wounds healing by secondary intention are thought to heal more slowly than wounds healing by primary intention, especially if infection is present or healing is compromised by factors such as decreased blood supply, poor nutritional status or a general suppression of the immune response. Such wounds may contain dead tissue and have a moderate or high level of exudate. Debridement involves the removal of devitalised, necrotic tissue or fibrin from a wound. There are many different methods that can be used to debride a wound, which are broadly classified as surgical/sharp, biosurgical, mechanical, chemical, enzymatic and autolytic. Although it is generally agreed that the management of surgical wounds which contain devitalised tissue and are healing by secondary intention requires debridement, it is not always clear as to what is the best method or agent to use. There is currently a large selection of products with debriding properties available on the market, which vary considerably in cost. It is important that the choice of both debriding method and product is based on the best scientific evidence available, taking into account both cost and effectiveness data. OBJECTIVES: The review had two main objectives: (1) To determine the clinical effectiveness and cost-effectiveness of debriding agents in treating surgical wounds healing by secondary intention. (2) To evaluate the clinical effectiveness and cost-effectiveness of treating patients with surgical wounds healing by secondary intention at specialised wound care clinics as compared to conventional care. The review incorporated all debriding methods and any agent that is considered to have a debriding property. METHODS The following databases were searched using strategies designed specifically for each database: MEDLINE, EMBASE, CINAHL, HMIC (Health Management Information Consortium), CCTR via the Cochrane Library, the National Research Register (NRR), the NHS Economic Evaluation Database (NHS EED), and the Health Economic Evaluations Database (HEED). Additional references were identified through reviewing manufacturer and sponsor submissions made to NICE, the bibliographies of retrieved articles, and conferences proceedings on the Internet. Only randomised controlled trials (RCTs) or non-randomised controlled trials with concurrent controls and full economic evaluations were considered for inclusion. Only studies that evaluated some sort of debriding method or a specialised wound care clinic (a nurse with specialist training in wound care; care being provided by a multidisciplinary team; a fast-track referral system to other professions (e.g. dermatologist); or access to the latest health technology) were included in the review. Studies had to include participants with surgical wounds healing by secondary intention (e.g. cavity wounds, the consequences of wound dehiscence and abscesses) and report an objective measure of wound healing. Data were extracted by one reviewer and checked by a second. Quality assessment was conducted independently by two reviewers. Disagreements were resolved by consensus and, when necessary, by recourse to a third reviewer. The primary outcomes of interest were wound healing and cost. Results of data extraction and quality assessment were presented in structured tables and also as a narrative summary. In addition, where feasible, the results of individual studies were presented as forest plots. Studies were grouped according to the type of wound, debriding method and outcome measure used. RESULTS - CLINICAL EFFECTIVENESS: Seventeen trials met the inclusion criteria, all of which used the autolytic method of debridement. No studies were found that investigated sharp/surgical, biosurgical, mechanical, chemical or enzymatic debridement in the treatment of surgical wounds healing by secondary intention. No studies were found which investigated specialised wound care clinics that included the provision of care within a clinical setting (based in either primary or secondary care). The type of surgical wounds investigated by studies included in the review were those that had broken down postoperatively, perineal wounds resulting from proctolectomy or rectal excision, and those left open after pilonidal sinus excision or abscess incision, or wounds following a laparotomy. Four additional studies investigated treatment of postoperative wounds from toenail avulsions. (ABSTRACT TRUNCATED)

Clinical Trials as Topic↗

Ecdysteroid agonist and antagonist activities in species of the Solanaceae.

Previously, it has been shown that certain withanolides from Iochroma gesnerioides (Solanaceae) possess ecdysteroid antagonistic activity. Phytoecdysteroids (agonists) are widely distributed in the plant world, but solanaceous species have not been extensively examined for their presence. We have now surveyed 128 species of solanaceous plants for the presence of ecdysteroid agonist and antagonist activities using the Drosophila melanogaster B(II) cell line bioassay. Only weak antagonistic activity was associated with a few of the methanolic extracts, including those from species known to contain high levels of withanolides. Therefore, the major withanolides are inactive per se, but they may be activated after ingestion by invertebrate predators. Several extracts possessed ecdysteroid agonist activity as a consequence of the presence of phytoecdysteroids. Phytoecdysteroid-accumulating species are at least as common in the Solanaceae as they are in plants in general. Preliminary characterization of the identities of the phytoecdysteroids present in the most active extracts has been performed by hplc separations on normal- and reversed-phase systems in conjunction with ecdysteroid-specific radioimmunoassay and bioassay. Each of the phytoecdysteroid-accumulating species examined (Browallia speciosa, Nierembergia hippomanica var violacea, N. solanacea and Solanum nigrum) contain a cocktail of ecdysteroids, of which 20-hydroxyecdysone and polypodine B (5beta,20-dihydroxyecdysone) are major components.

Journal Article↗

Identification of a GABAB receptor subunit, gb2, required for functional GABAB receptor activity.

G protein-coupled receptors are commonly thought to bind their cognate ligands and elicit functional responses primarily as monomeric receptors. In studying the recombinant gamma-aminobutyric acid, type B (GABAB) receptor (gb1a) and a GABAB-like orphan receptor (gb2), we observed that both receptors are functionally inactive when expressed individually in multiple heterologous systems. Characterization of the tissue distribution of each of the receptors by in situ hybridization histochemistry in rat brain revealed co-localization of gb1 and gb2 transcripts in many brain regions, suggesting the hypothesis that gb1 and gb2 may interact in vivo. In three established functional systems (inwardly rectifying K+ channel currents in Xenopus oocytes, melanophore pigment aggregation, and direct cAMP measurements in HEK-293 cells), GABA mediated a functional response in cells coexpressing gb1a and gb2 but not in cells expressing either receptor individually. This GABA activity could be blocked with the GABAB receptor antagonist CGP71872. In COS-7 cells coexpressing gb1a and gb2 receptors, co-immunoprecipitation of gb1a and gb2 receptors was demonstrated, indicating that gb1a and gb2 act as subunits in the formation of a functional GABAB receptor.

Amino Acid Sequence↗

Cloning of a novel G-protein-coupled receptor GPR 51 resembling GABAB receptors expressed predominantly in nervous tissues and mapped proximal to the hereditary sensory neuropathy type 1 locus on chromosome 9.

Query of the expressed sequence tag database with the rat metabotropic GABABR1A receptor amino acid sequence using the TFASTA algorithm revealed two partial cDNA fragments whose sequence information was then used to isolate by PCR a novel full-length human cDNA encoding a putative G-protein-coupled receptor (GPCR), termed GPR 51. Sequence analysis revealed that it encoded a protein of 941 amino acids, similar in size and homology to GABAB receptors followed by metabotropic glutamate receptors but not other GPCRs. GPR 51 expressed in COS-1 cells showed no specific binding for [3H](+)baclofen and when expressed in Xenopus oocyte and Xenopus melanophore functional assays showed no activity to GABA, (-)baclofen, and glutamic acid. Northern blot analysis and in situ hybridization revealed that GPR 51 transcripts were predominantly expressed in the central nervous system with highest abundance in the cortex, thalamus, hippocampus, amygdala, cerebellum, and spinal cord. In contrast, GPR 51 receptor transcripts were almost not detected in the peripheral tissues. Gene GPR 51 was localized by radiation hybrid mapping to chromosome 9, 4.81 cR from the WI-8684 marker, and proximal to the hereditary sensory neuropathy type 1 locus.

Amino Acid Sequence↗

Phytoecdysteroids in seeds and plants of Rhagodia baccata (Labill.) Moq. (Chenopodiaceae).

Seeds of Rhagodia baccata afforded, in addition to 20-hydroxy-ecdysone and polypodine B, a novel phytoecdysteroid, (20R)-22-deoxy-20,21-dihydroxyecdysone, the structure of which was elucidated unequivocally by UV, LSIMS and NMR techniques. This compound possessed agonistic activity in the Drosophila melanogaster BII cell bioassay, with an ED50 value of 2.0 x 10(-7)M (ED50 value for 20-hydroxyecdysone = 7.5 x 10(-9)M). The distribution of ecdysteroids in plants of R. baccata has been determined. Highest levels are associated with the youngest aerial tissues and with the roots. Ecdysteroid profiles are qualitatively very similar throughout the plant, with 20-hydroxyecdysone and polypodine B predominating in all plant parts tested.

Animals↗

Influenza activity in England and Wales: October 1998 to June 1999.

Influenza activity in England and Wales in the winter of 1998/1999 reached the highest weekly levels seen since the epidemic of 1989/1990. Activity peaked at Christmas and the New Year, adding to the winter pressures on general practitioner and hospital services. Adults aged 65 years and over consulted with general practitioners at the highest rates. Outbreaks of influenza or flu-like illness occurred in several schools and nursing homes and, in June 1999, on a British cruise ship in the Mediterranean. Deaths from all causes reached a higher peak in week 1 of 1999 than occurred in the peak week of the influenza epidemic of 1989/90.

Adolescent↗

Cucurbitacins are insect steroid hormone antagonists acting at the ecdysteroid receptor.

Two triterpenoids, cucurbitacins B and D, have been isolated from seeds of Iberis umbellata (Cruciferae) and shown to be responsible for the antagonistic activity of a methanolic extract of this species in preventing the 20-hydroxyecdysone (20E)-induced morphological changes in the Drosophila melanogaster BII permanent cell line. With a 20E concentration of 50 nM, cucurbitacins B and D give 50% responses at 1.5 and 10 microM respectively. Both cucurbitacins are able to displace specifically bound radiolabelled 25-deoxy-20-hydroxyecdysone (ponasterone A) from a cell-free preparation of the BII cells containing ecdysteroid receptors. The Kd values for cucurbitacins B and D (5 and 50 microM respectively) are similar to the concentrations required to antagonize 20E activity with whole cells. Cucurbitacin B (cucB) prevents stimulation by 20E of an ecdysteroid-responsive reporter gene in a transfection assay. CucB also prevents the formation of the Drosophila ecdysteroid receptor/Ultraspiracle/20E complex with the hsp27 ecdysteroid response element as demonstrated by gel-shift assay. This is therefore the first definitive evidence for the existence of antagonists acting at the ecdysteroid receptor. Preliminary structure/activity studies indicate the importance of the Delta23-22-oxo functional grouping in the side chain for antagonistic activity. Hexanorcucurbitacin D, which lacks carbon atoms C-22 to C-27, is found to be a weak agonist rather than an antagonist. Moreover, the side chain analogue 5-methylhex-3-en-2-one possesses weak antagonistic activity.

Animals↗

Two limonoids from Turraea obtusifolia (Meliaceae), prieurianin and rohitukin, antagonise 20-hydroxyecdysone action in a Drosophila cell line.

Bioassay-assisted HPLC analyses yielded two prieurianin-type limonoids, prieurianin and rohitukin, from the seeds of Turraea obtusifolia, which act as antagonists of 20-hydroxyecdysone action in the Drosophila melanogaster BII cell line. With a 20-hydroxyecdysone concentration of 5 x 10(-8) M, the ED50 values for prieurianin and rohitukin are 10(-5) M and 1.25 x 10(-4) M, respectively.

Animals↗

Endogenous ecdysteroid levels and rates of ecdysone acylation by intact ovaries in vitro in relation to ovarian development in adult female crickets, Acheta domesticus.

Ecdysteroid titres have been determined in adult female house crickets (Acheta domesticus) in relation to reproductive maturation. Ecdysteroid levels in newly emerged adult females are low except in the gut and carcass, which probably reflects the remnants of the preecdysial ecdysteroid peak. Ecdysteroid levels in all compartments increase markedly once ovarian weight surpasses 10 mg. Apolar ecdysteroid conjugates (ecdysone 22-fatty acyl esters) predominate in ovarian tissue throughout ovarian maturation, but low levels of free ecdysteroid and polar conjugated ecdysteroids are also present. During this period, two peaks of ecdysteroids (mainly free and apolar conjugated ecdysteroids) are observed in the haemolymph, gut, and carcass compartments. The peaks in the haemolymph occur when the ovarian mass reaches 30 and 100 mg. The gut and carcass may be acting as sinks or sites of metabolism for the hormone released from the ovaries. The rate of ecdysone acylation by ovaries was found to be developmentally regulated, increasing from low levels in the immature ovaries of newly emerged females as the ovaries increase in size. A semiquantitative assay has been developed to identify compounds which inhibit the conversion of [3H]ecdysone into 22-fatty acyl [3H]ecdysone by ovaries in vitro. A number of ecdysteroids possessing a free hydroxyl group as C-22 as well as the side-chain stereochemistry of ecdysone effectively inhibit this conversion, probably by acting as competitive substrates. In the cases of 20-hydroxyecdysone and ponasterone A, it was clearly demonstrated that these compounds are converted to a mixture of C-22 fatty acyl esters. Several other compounds which have been suggested to affect ecdysteroid metabolism/mode of action in other systems were also tested for their effects on the acyltransferase activity of ovaries in vitro.

Acylation↗

Cucurbitane-type compounds from Hemsleya carnosiflora antagonize ecdysteroid action in the Drosophila melanogaster BII cell line.

The ecdysteroid agonist and antagonist activities of 3 cucurbitanes, 2 cucurbitane glycosides and 2 cucurbitacins isolated from Hemsleya carnosiflora (Cucurbitaceae) have been determined in the Drosophila melanogaster BII bioassay. Carnosiflogenins A and C and carnosiflosides II and VI possess antagonistic activity. Carnosiflogenin A was also found to induce the formation of spindle-shaped cells with high frequency in both the agonist and antagonist assays. At 10(-3) M, carnosiflogenins B and C were cytotoxic, 23,24-Dihydrocucurbitacin F and 25-acetoxy-23,24-dihydrocucurbitacin F are also antagonistic at high concentrations. The concentration dependencies of the antagonistic activities of these two cucurbitacins, carnosiflosides II and VI and carnosiflogenin C are presented. The biological and ecological significance of these results are discussed in relationship to the concentrations present in the rhizomes of H. carnosiflora.

Animals↗

Tyrosine kinase phosphorylation of GABAA receptors.

Phosphorylation of purified bovine brain GABAA receptors by the tyrosine kinase, pp60v-src was examined. pp60v-src phosphorylated two bands of 54-62 kDa and 48-51 kDa that migrated to approximately the same position as bands recognized by antisera against the beta 2 and gamma 2 GABAA receptor subunits, respectively. Bacterially expressed proteins containing the putative large cytoplasmic loops of the beta 1 and gamma 2L subunits were phosphorylated by pp60v-src, indicating that the phosphorylation sites are located in these subunit domains. The tyrosine kinase inhibitors, genistein and the tyrphostins B-42 and B-44, inhibited muscimol-stimulated 36Cl- uptake in mouse brain membrane vesicles (microsacs). magnitude of the tyrphostin B-44-induced inhibition of muscimol-stimulated 36Cl- uptake was significantly reduced in microsacs that were lysed and resealed under conditions that inhibit phosphorylation. GABA-gated Cl- currents were also inhibited by genistein and tyrphostin B-44 in Xenopus oocytes expressing alpha 1 beta 1 and alpha 1 beta 1 gamma 2L subunits. Consequently, protein tyrosine kinase-dependent phosphorylation appears to be another mechanism of regulating the function of GABAA receptors.

Animals↗