Biomedical subjects
Publications and source records attributed to Sarah Jones.
We describe an 80-year-old lady with a meningoencephalitic illness followed by vertebral discitis. Enterococcus avium was cultured from her cerebrospinal fluid. No other pathogen was incriminated in her illness. The meningoencephalitic illness settled after 3 weeks of antimicrobials, but the vertebral discitis required longer therapy.
The receptor mimetic and mast cell degranulating peptide mastoparan (MP) translocates cell membranes as an amphipathic alpha-helix, a feature that is undoubtedly a major determinant of bioactivity through the activation of heterotrimeric G proteins. Chimeric combinations of MP with G protein-coupled receptor (GPCR) ligands has produced peptides that exhibit biological activities distinct from their composite components. Thus, chimeric peptides such as galparan and M391 differentially modulate GTPase activity, display altered binding affinities for appropriate GPCRs and possess disparate secretory properties. MP and MP-containing chimerae also bind and modulate the activities of various other intracellular protein targets and are valuable tools to manipulate and study enzymatic activity, calcium homeostasis and apoptotic signalling pathways. In addition, charge delocalisation within the hydrophilic face of MP has produced analogues, including [Lys5, Lys8,Aib10]MP, that differentially regulate mast cell secretion and/or cytotoxicity. Finally, the identification of cell penetrant variants of MP chimerae has enabled the effective intracellular delivery of non-permeable biomolecules and presents an opportunity to target novel intracellular therapeutic loci.
AIM: to explore whether nurses can undertake the pre operative assessment of children prior to day case surgery as safely as senior house officers. DESIGN: a randomised controlled trial involving 595 children, using an equivalence methodology (a method which looks for similarity rather than a significant difference). Pre-operative assessment prior to day case surgery was randomised to either a nurse (experimental group) or a junior doctor (control group). Blinded expert verification of nurse/junior doctor performance was ascertained by an experienced anaesthetist (the 'gold standard'). RESULTS: there was equivalence between nurses and senior house officers in their ability to detect clinically significant abnormalities within the sample population. Subgroup analysis also demonstrated equivalence in respect of history taking abilities. The smaller number of clinically significant physical findings within the sample meant that equivalence in respect of physical examination remains uncertain. Although the study was limited to a single setting, the results demonstrate nurses' equivalence with junior doctors in a discrete paediatric context.
The carboxyl terminal of heterotrimeric G protein alpha subunits binds both G protein-coupled receptors and mastoparan (MP), a tetradecapeptide allostere. Moreover, peptides corresponding to the carboxyl domains of G(i)3alpha and G(t) display intrinsic biological activities in cell-free systems. Thus, the purpose of this study was to develop a cell penetrant delivery system to further investigate the biological properties of a peptide mimetic of the G(i)3alpha carboxyl terminal (G(i)3alpha(346-355); H-KNNLKECGLY-NH2). Kinetic studies, using a CFDA-conjugated analogue of G(i)3alpha(346-355), confirmed the rapid and efficient intracellular translocation of TP10-G(i)3alpha(346-355) (t(0.5) = 3 min). Translocated G(i)3alpha(346-355), but not other bioactive cargoes derived from PKC and the CB1 cannabinoid receptor, promoted the dual phosphorylation of p42/p44 MAPK without adverse changes in cellular viability. The relative specificity of this novel biological activity was further confirmed by the observation that translocated G(i)3alpha(346-355) did not influence the exocytosis of beta-hexoseaminidase from RBL-2H3, a secretory event stimulated by other cell penetrant peptide cargoes and MP. We conclude that TP10-G(i)3alpha(346-355) is a valuable, non-toxic research tool with which to study and modulate signal transduction pathways mediated by heterotrimeric G proteins and MAPK.
Nitric oxide (NO) is pivotal to bone physiology. In the central nervous system constitutive, Ca(2+)-calmodulin regulated NO synthase activity and glutamate signalling are intimately linked. Since L-glutamate signalling occurs in bone and is implicated in bone regulation, we have investigated the effect of L-glutamate on NO synthase in bone-derived cells. Treatment of marrow stromal cells with L-glutamate reduced basal NO synthase activity by 40%. Imaging showed that L-glutamate caused a rapid, usually localised and slowly-reversible fall in [Ca(2+)](i). This effect was resistant to disruption of intracellular Ca(2+) stores but sensitive to extracellular La(3+) or omission of extracellular Ca(2+), demonstrating that glutamate acts by inhibition of membrane Ca(2+) influx. The only previous description of such an effect of L-glutamate is via activation of the group III receptor, mGluR6, in the retina. Using Western blotting and RT-PCR we detected mGluR6 protein and transcripts in marrow stromal cells. The effects of L-glutamate on NOS activity and [Ca(2+)](i) in marrow stromal cells were abolished by a group III mGluR inhibitor, (S)-2-amino-2-methyl-4-phosphonobutyric acid. Recording of membrane potential showed that, similarly to the effects of retinal mGluR6 activation, L-glutamate induced membrane hyperpolarisation (-16 +/- 2 mV), which was also sensitive to group III mGluR inhibition. L-glutamate had no effect on cAMP levels. We conclude that activation of a group III mGluR in bone marrow stromal cells inhibits a Ca(2+)-permeable plasma membrane channel, reducing [Ca(2+)](i) and suppressing generation of NO. These observations directly link bone L-glutamate signalling to processes central to bone growth and regulation.
The formation of an amphipathic helix is a major determinant of the biological activity of the tetradecapeptide mastoparan (MP). To address the functional significance of lysyl residues at positions 4, 11 and 12 of MP, we synthesised five novel analogues using sequence permutation and arginine-substitution to delocalise cationic charge. Comparative bioassays determined cytotoxicity, beta-hexoseaminidase secretory efficacy and peptide-activated extracellular receptor-stimulated kinase (ERK)1/2 phosphorylation. The monosubstitution of individual lysine residues with arginine produced differential changes to the indices of cytotoxicity and secretion indicating that these conservative substitutions are compatible with membrane translocation and the selective binding and activation of intracellular proteins. More profound changes to the predicted hydrophilic face of MP, resulting from the relocation or substitution of additional lysyl residues, enhanced both the cytotoxicity and secretory efficacy of novel peptides. Significantly, the more amphipathic peptide [Lys5, Lys8, Aib10]MP was identified to be both the most cytotoxic and the most potent secretagogue of all the peptides compared here. Charge delocalisation within the hydrophilic face of MP analogues was also compatible with peptide-induced activation of ERK1/2 phosphorylation. Our data indicate that charge delocalisation is a suitable strategy to engineer more potent analogues of MP that differentially target intracellular proteins.
Lifestyle factors such as diet and physical activity vary in different social and income groups, and are known to be important influences on the incidence of osteoporotic fractures. Financial and social pressures are a common concern for older people. We set out to study the effect of socioeconomic deprivation on the incidence of fracture in older people and to compare the findings with those for younger groups. The All Wales Injury Surveillance System (AWISS) is a computerized system that collects injury data from most A&E departments throughout Wales. In this population-based study of 1.8 million people living in the 445 electoral tracts covered by AWISS in south, west, and northeastern Wales, we identified all 60,106 residents who presented with a fracture in 1999 and 2000. We linked details of their fracture with published Townsend deprivation scores for the electoral tract in which they were living and calculated fracture rates by fifths of deprivation. We observed the expected pattern of increasing fracture incidence in older age groups. Fracture incidence was significantly higher in electoral wards with poorer Townsend scores, resulting from a marked effect of socioeconomic deprivation on fracture incidence among younger adults with a rate ratio of 1.64 (95% CI, 1.57 to 1.72). This effect diminished with age, and was not observed in older age groups. At ages 85 and over the rate ratio was 0.94 (95% CI, 0.87 to 1.01). Socioeconomic factors clearly play a part in the causation of fracture in younger adults. Lifestyle influences are important in older age groups, but socioeconomic deprivation does not appear to be a risk factor for the development of osteoporotic fractures in elderly people.
This investigation compared the secretory efficacies of a series of peptides delivered to the cytoplasm of RBL-2H3 mast cells. Mimetic peptides, designed to target intracellular proteins that regulate cell signalling and membrane fusion, were synthesised as transportan 10 (TP10) chimeras for efficient plasma membrane translocation. Exocytosis of beta-hexosaminidase, a secretory lysosomal marker, indicated that peptides presenting sequences derived from protein kinase C (PKC; C1 H-CRRLSVEIWDWDL-NH(2)) and the CB(1) cannabinoid receptor (C3 H-RSKDLRHAFRSMFPSCE-NH(2)) induced beta-hexosaminidase secretion. Other peptide cargoes, including a Rab3A-derived sequence and a homologue of C3, were inactive in similar assays. Translocated C1 also activated phospholipase D (PLD), an enzyme intimately involved in the regulated secretory response of RBL-2H3 cells, but C1-induced secretion was not dependent upon phosphatidate synthesis. Neither down-regulation of Ca(2+)-sensitive isoforms of PKC nor the application of a selective PKC inhibitor attenuated the secretory efficacy of C1. These observations indicate that the molecular target of C1 is a protein involved in the regulated secretory pathway that is upstream of PLD but is not a PKC isoform. This study also confirmed that TP10 is a relatively inert cell-penetrating vector and is, therefore, widely suitable for studies in cells that are sensitive to peptidyl secretagogues.
Fracture prevention strategies will be most cost-effective if targeted on groups of frail elderly people who are at particularly high risk of falls and fractures. Elderly people living in care homes are one potential target population, but fracture incidence in this setting remains poorly defined in many countries. We used the All Wales Injury Surveillance System (AWISS) in a population-based study of people aged over 65 years living in the city of Cardiff. We linked a postcode-based register of all sheltered accommodation and all residential and nursing homes in the city with injury data from Cardiff's single Accident and Emergency Department. Cardiff has 47,700 residents aged over 65 years with 1918 (4.0%) living in residential or nursing homes and 1868 (3.9%) in sheltered accommodation. In 1999 we identified a total of 1305 fractures including 366 hip fractures, giving a crude fracture incidence of 27.4/1000 per year and 7.7/1000 per year, respectively. Care home residents suffered 213 fractures, 95 of which were of the hip, giving a crude fracture incidence of 111.1/1000 per year and 49.5/1000 per year, respectively. People living in sheltered accommodation suffered 94 fractures, including 28 at the hip, giving a crude fracture incidence of 51.4/1000 per year and 15.3/1000 per year, respectively. People in care homes and sheltered accommodation tend to be older than those living in the community, and we adjusted for this by calculating age- and gender-standardized relative ratios for each setting. Compared with the community dwelling population, care home residents had an overall fracture risk of 2.9 (95% CI 2.5-3.3) and a hip fracture risk of 3.3 (95% CI 2.6-4.2). People in sheltered accommodation had a total fracture risk of 1.7 (95% CI 1.4-2.1), and a hip fracture risk of 1.6 (95% CI 1.1-2.4). Such figures support the potential cost-effectiveness of strategies that seek to prevent fractures in care homes and sheltered accommodation, and are of special interest to those planning intervention studies in these settings.
We have used the All Wales Injury Surveillance System (AWISS) in a population-based study of wrist and forearm fractures. We examined seasonal variation in the incidence of these injuries, and looked at resulting pressures on outpatient and inpatient trauma services. AWISS collected data from eight Accident and Emergency (A&E) departments which between them serve a total of 1.2 million people in South Wales. During a single year, we identified all 5013 people who presented with a wrist or forearm fracture. Seasonal variation in wrist/forearm fracture incidence was apparent, but showed a different pattern in different age groups. Overall incidence figures were dominated by an increase in children's fractures in spring and summer. Children under the age of 15 suffered a total of 360 wrist and forearm fractures during the three winter months; an incidence of 5.9/1000 per year that was only about half that observed during the remainder of the year (10.7/1000 per year). In contrast, older people showed a higher incidence in the winter. During the winter months people aged over 75 sustained a total of 160 wrist/forearm fractures; an incidence of 8.2/1000 per year, significantly higher than the incidence observed in other months (5.8/1000 per year). Seasonality of incidence was not apparent in other age groups. Children presenting during the spring and summer months were significantly more likely to need admission to hospital; 22.8% were admitted compared with just 10.3% of those presenting during the winter months (P<0.001, chi(2)-test). Other age groups showed no significant seasonal variation in the likelihood of hospital admission.
Despite the rapid growth of research on neighborhood influences on children, little of this research may be useful to prevention scientists. Most studies have ignored processes by which neighborhood conditions influence individual outcomes. To encourage neighborhood research that can better guide the development of preventive interventions, we propose a model that focuses attention on mediating and moderating processes, is appropriate for studies interested in individual differences in outcomes, acknowledges the transactions between residents and neighborhoods, and is sensitive to how neighborhood influences may differ for children at different developmental stages. Furthermore, we argue that greater attention to several methodological issues also can make neighborhood research more useful for the next generation of prevention programs to help low-income urban families and children cope successfully with the challenges posed by their neighborhoods.
The past decade has witnessed a rapid expansion of our understanding of the biological roles of cannabinoids and their cognate receptors. It is now certain that Delta9-tetrahydrocannabinol, the principle psychoactive component of the Cannabis sativa plant, binds and activates membrane receptors of the 7-transmembrane domain, G-protein-coupled superfamily. Several putative endocannabinoids have since been identified, including anandamide, 2-arachidonyl glycerol and noladin ether. Synthesis of numerous cannabinomimetics has also greatly expanded the repertoire of cannabinoid receptor ligands with the pharmacodynamic properties of agonists, antagonists and inverse agonists. Collectively, these ligands have proven to be powerful tools both for the molecular characterisation of cannabinoid receptors and the delineation of their intrinsic signalling pathways. Much of our understanding of the signalling mechanisms activated by cannabinoids is derived from studies of receptors expressed by tumour cells; hence, this review provides a succinct summary of the molecular pharmacology of cannabinoid receptors and their roles in tumour cell biology. Moreover, there is now a genuine expectation that the manipulation of cannabinoid receptor systems may have therapeutic potential for a diverse range of human diseases. Thus, this review also summarises the demonstrated antitumour actions of cannabinoids and indicates possible avenues for the future development of cannabinoids as antitumour agents.
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Plasma concentrations of enrofloxacin and its active metabolite ciprofloxacin were monitored following oral administration of enrofloxacin at 7.5, 10, and 20 mg/kg to six healthy female bloodhounds using a randomized crossover design. Plasma samples were collected at various times over 24 hours following drug administration. Both the parent drug and its metabolite were detected by high-performance liquid chromatography, and plasma drug concentration-versus-time curves were subjected to noncompartmental pharmacokinetic analysis. Descriptive statistics were determined for each dosage, and comparisons were made among dosage groups for selected pharmacokinetic parameters. Increasing dosages of enrofloxacin resulted in increased plasma concentrations of both enrofloxacin and ciprofloxacin. Maximum concentration (Cmax) was 2.12 +/- 0.59, 2.1 +/- 0.34, and 4.74 +/- 1.05 mcg/ml for enrofloxacin and 1.30 +/- 0.31, 1.30 +/- 0.32, and 1.86 +/- 0.35 mcg/ml for ciprofloxacin when enrofloxacin was given at dosages of 7.5, 10, and 20 mg/kg, respectively. Cmax and area under the curve (AUC) for both enrofloxacin and ciprofloxacin were significantly greater at 20 mg/kg than at 7.5 and 10 mg/kg. Disappearance half-life was similar for all dosages, ranging from 4.6 to 5.2 hours for enrofloxacin and 8.8 to 10.7 hours for ciprofloxacin. Ciprofloxacin contributed up to 42% of the Cmax and up to 55% of the AUC of the total (enrofloxacin plus ciprofloxacin). For organisms with a minimum inhibitory concentration (MIC) of 0.5 mcg enrofloxacin/ml, an inhibitory quotient (IQ; Cmax:MIC) of 8 or more was achieved in plasma only at 20 mg/kg.
Exercise testing commonly used by clinicians to characterize cardiovascular risk by detecting myocardial ischemia and assessing response to exercise. However, a consensus has not previously existed regarding the significance of exercise test-induced arrhythmias due to conflicting results from the available studies. Recent studies with longer follow-up and improved technology have therefore stimulated this current review of the topic. Despite the continued debate in the literature regarding the prognosis of ETIA in a general population, there is sufficient evidence to suggest that clinicians should closely evaluate and follow those patients with arrhythmias during exercise testing and aggressively modify risk factors for coronary artery disease.
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