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Biomedical subjects

H J Taylor

Publications and source records attributed to H J Taylor.

15 recordsLinked to original sources
PubMed2001

Gap junction-dependent increases in smooth muscle cAMP underpin the EDHF phenomenon in rabbit arteries.

We have investigated the role of cAMP in nitric oxide (NO)- and prostanoid-independent vascular relaxations evoked by acetylcholine (ACh) in isolated arteries and perfused ear preparations from the rabbit. These EDHF-type responses are shown to be associated with elevated cAMP levels specifically in smooth muscle and are attenuated by blocking adenylyl cyclase or protein kinase A (PKA). Relaxations are amplified by 3-isobutyl-1-methylxanthine, which prevents cAMP hydrolysis, while remaining susceptible to inhibition by the combination of two K(Ca) channel blockers, apamin and charybdotoxin. Analogous endothelium- and cAMP-dependent relaxations were evoked by cyclopiazonic acid (CPA) which stimulates Ca(2+) influx via channels linked to the depletion of Ca(2+) stores. Responses to ACh and CPA were both inhibited by interrupting cell-to-cell coupling via gap junctions with 18alpha-glycyrrhetinic acid and a connexin-specific Gap 27 peptide. The findings suggest that EDHF-type responses are initiated by capacitative Ca(2+) influx into the endothelium and propagated by direct intercellular communication to effect relaxation via cAMP/PKA-dependent phosphorylation events in smooth muscle.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Effect of sonic and mechanical toothbrushes on subgingival microbial flora: a comparative in vivo scanning electron microscopy study of 8 subjects.

OBJECTIVES: The purpose of this initial study was to evaluate the effects of both a sonic and a mechanical toothbrush versus the effects of no treatment on depth of subgingival penetration of epithelial and tooth-associated bacteria. METHOD AND MATERIALS: Eight adult subjects exhibiting advanced chronic periodontitis with at least 3 single-rooted teeth that were in separate sextants with facial pockets > or = 4 mm and < or = 8 mm and that required extraction constituted the experimental sample. Teeth were either subjected to 15 seconds of brushing with a mechanical toothbrush or a sonic toothbrush or left untreated. The test tooth and the associated soft tissue wall of the periodontal pocket were removed as a single unit. Samples were processed and coded for blind examination by scanning electron microscopy. Distributional and morphologic characteristics of dominant bacteria with specific emphasis on spirochetes were evaluated for both epithelial- and tooth-associated plaque. RESULTS: No differences were found in morphotypes or distributional and aggregational characteristics of epithelial-associated microbes in the 1- to 3-mm subgingival zone between the mechanical and sonic toothbrush-treated groups and the control group. Both toothbrush groups featured disruption of microbes that extended up to 1 mm subgingivally. Root surfaces on the sonic-treated samples appeared plaque-free at low magnification; however, at 4,700x, a thin layer of mixed morphotypes and intact spirochetes was found subgingivally and slightly subgingivally. In comparison, mechanical brush samples featured incompletely removed plaque, both subgingivally and subgingivally, with intact spirochetes present on subgingival root surfaces. CONCLUSION: Results suggest similar effects for both sonic and mechanical toothbrushes on epithelial- and tooth-associated bacterial plaque in periodontal pockets and adjacent root surfaces that extend up to 1 mm subgingivally. Further, the presence of intact subgingival spirochetes suggests limited exposure to acoustical or mechanical energy from the toothbrushes evaluated.

Acoustics↗
PubMed2000

Secondary acute myeloblastic leukaemia (AML) (expressing 11q23 mutation) occurring 11 months after chemotherapy/radiotherapy for paediatric non-Hodgkin lymphoma (NHL).

The occurrence of 11q23 cytogenetic abnormalities in drug-induced acute myeloid leukaemia (AML) is now well recognized. They are most frequently associated with topoisomerase II inhibitor administration. We here describe the case history of a 15-year-old child who presented with Stage III B-cell non-Hodgkin's lymphoma (NHL) and was treated with anthracyclines, alkylating agents and low-dose mediastinal radiotherapy. She developed an 11q23 mutation-related secondary AML at 11 months after therapy (15 months after her first exposure to drugs; 12 months after the first radiotherapy exposure), possibly the earliest yet reported in a paediatric patient. We discuss this newly recognized early form of refractory, secondary AML and its relationship to chemoradiotherapy.

Adolescent↗
PubMed1999

Cyclic AMP mediates EDHF-type relaxations of rabbit jugular vein.

Isolated rings of rabbit jugular vein have been used to test the hypothesis that formation of cAMP within the endothelial cell contributes to relaxations that are attributable to the endothelium-derived hyperpolarizing factor, EDHF. Relaxations induced by acetylcholine under conditions of combined NO synthase and cyclooxygenase blockade were almost abolished by inhibition of adenylate cyclase with the selective P-site agonist 2', 3'-dideoxyadenosine (2',3'-DDA). They were similarly attenuated by the gap junction inhibitors 18alpha-glycyrrhetinic acid (18alpha-GA) and Gap 27 peptide which interrupt direct endothelium-smooth muscle communication without themselves affecting smooth muscle tone. By contrast, stimulation of adenylate cyclase with forskolin promoted gap junction-dependent relaxations, with concentration-relaxation curves to this agent exhibiting an equivalent rightward shift in the presence of 18alpha-GA and following endothelial denudation. The findings suggest that cAMP may cross from the endothelium to smooth muscle via gap junction channels and/or enhance the endothelial hyperpolarization normally associated with agonist stimulation. Both mechanisms may contribute to EDHF/gap junction-dependent relaxations.

Acetylcholine↗
PubMed1999

Evaluation of a rapid and inexpensive dipstick assay for the diagnosis of Plasmodium falciparum malaria.

Rapid, accurate and affordable methods are needed for the diagnosis of malaria. Reported here is an evaluation of a new immunochromatographic strip, the PATH Falciparum Malaria IC Strip, which is impregnated with an immobilized IgM monoclonal antibody that binds to the HRP-II antigen of Plasmodium falciparum. In contrast to other commercially available kits marketed for the rapid diagnosis of falciparum malaria, this kit should be affordable in the malaria-endemic world. Using microscopy and polymerase chain reaction (PCR)-based methods as reference standards, we compared two versions of the PATH test for the detection of P. falciparum infection in 200 febrile travellers. As determined by PCR and microscopy, 148 travellers had malaria, 50 of whom (33.8%) were infected with P. falciparum. Compared with PCR, the two versions of the PATH test had initial sensitivities of 90% and 88% and specificities of 97% and 96%, respectively, for the detection of falciparum malaria. When discrepant samples were retested blindly with a modified procedure (increased sample volume and longer washing step) the sensitivity and specificity of both kits improved to 96% and 99%, respectively. The two remaining false negatives occurred in samples with < 100 parasites per microliter of blood. The accuracy, simplicity and predicted low cost may make this test a useful diagnostic tool in malaria-endemic areas.

Antibodies, Monoclonal↗
PubMed1998

Inhibition of the gap junctional component of endothelium-dependent relaxations in rabbit iliac artery by 18-alpha glycyrrhetinic acid.

The gap junction inhibitor 18-alpha-glycyrrhetinic acid (alpha-GA, 100 microM) attenuated endothelium-dependent relaxations to acetylcholine and cyclopiazonic acid by approximately 20% in rings of pre-constricted rabbit iliac artery. The nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 300 microM) inhibited relaxations to both agents by approximately 65% and these were further attenuated by alpha-GA to < 10% of control. In endothelium-denuded preparations, relaxations to sodium nitroprusside were not affected by alpha-GA. Heterocellular gap junctional communication may therefore account for nitric oxide-independent relaxations evoked both by receptor-dependent and -independent mechanisms in rabbit iliac artery.

Acetylcholine↗
PubMed1995

A preventive child health program: the effect of telephone and home visits by public health nurses.

A randomized trial was conducted to determine if a public health nursing intervention consisting of telephone contacts or home visits affected the receipt of preventive health services by children eligible for the Early Periodic Screening, Diagnosis, and Treatment program. Each nursing intervention was applied using a protocol, and outcome data for 1654 case subjects were obtained from state-paid provider claims. However, the trial revealed no statistically significant differences between the study groups, nor was ethnicity a significant factor. Methodological and study context issues were identified that may have affected the results, the generalization of which is limited by the strict selection of cases.

Child↗
PubMed1992

Tolerance to SO2, NO2 and their mixture in Plantago major L. populations.

The possible evolution of tolerance to NO2, alone or in combination with SO2 was investigated in three populations of Plantago major L., originating from Hyde Park in central London (polluted site), Ascot (clean site) and The Netherlands. Screening for sensitivity to the pollutants was carried out by means of chronic fumigations with NO2 or NO2 plus SO2 and acute fumigations with SO2, NO2 or their mixture. The Hyde Park population showed smaller growth reductions induced by the pollutant mixture, than did the other populations. In contrast no differential response in terms of foliar injury was observed after an acute fumigation with SO2+ NO2, but the Hyde Park population was the most sensitive to NO2 alone. The results indicate that selection for tolerance to SO2 does not confer tolerance to NO2 alone or the pollutant mixture.

Journal Article↗
PubMed1985

Choice of analgesia/anaesthesia during labour and delivery.

Considerations for analgesic or anaesthetic intervention during labour and delivery are reviewed. The amelioration of maternal discomfort must be safe for both mother and fetus. The origin and consequences of labour pain are discussed. Maternal stress resulting from pain can adversely affect fetal oxygen supply. The pros and cons of systemic and regional analgesia are discussed.

Analgesia↗
PubMed1983

Clinical experience with continuous epidural infusion of bupivacaine at 6 ml per hour in obstetrics.

Maintenance of continuous epidural analgesia for obstetrics by slow infusion is a feasible alternative to maintenance by intermittent injection. The method described by Davies and Fettes using 0.25 per cent bupivacaine through a 6 ml/hr capillary flow device (Intraflo), with the fast-flush cut-off, is simple and convenient. However, failure of the fast-flush valve, resulting in a high flow rate, has been reported. It is therefore imperative that, prior to connecting the pressurized system to the epidural catheter, correct function of the device be verified by observing the flow rate in the microdrip chamber. We have used this method for the past year and found the equipment reliable, but in order to achieve more satisfactory analgesia the concentration of the infusion was increased initially to 0.375 per cent, and then reduced to 0.30 per cent. The records of the first 187 patients were reviewed retrospectively. Group I (n = 99) received an infusion of 0.25 per cent bupivacaine, Group II (n = 49) received 0.30 per cent and Group II (n = 39) received 0.375 per cent. Significantly more patients in Group I (30 per cent) required supplementary top-ups (in addition to the infusion) for the first stage of labour than in either Group II (10 per cent), or Group III (13 per cent). Top-ups for delivery were given to 55 per cent of patients in Group I, 64 per cent in Group II and 48 per cent in Group III. The incidence of motor block was significantly higher in Group III (21 per cent) than in either Group I (1 per cent) or Group II (2 per cent). For continuous epidural infusion at 6 ml/hr, 0.30 per cent bupivacaine combines optimum analgesia with minimal side-effects.

Adult↗