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Wang L, Davis MJ. Permanent pacing system malfunction due to hidden adjacent fractures of atrial and ventricular leads. Int J Cardiol 1997; 59:85-7. [PMID: 9080029 DOI: 10.1016/s0167-5273(96)02890-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Periods of failure of ventricular pacing and atrial sensing were discovered on Holter recording in a 10-year-old boy 4 years after the implantation of a dual-chamber pacemaker with endocardial bipolar leads brought out through the right atrial wall. The old generator was explanted and the old leads tested. There was considerable atrial oversensing of an electrical artefact. The pacing threshold of ventricular lead was 1.8 V compared with 0.3 V 6 days post implantation. Post-operative lateral chest X-ray disclosed fractures of both atrial and ventricular leads at the approximate site of exit from the right atriotomy. Review of the preoperative lateral film showed that the fractures had been hidden by an ECG electrode.
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Muller JM, Chilian WM, Davis MJ. Integrin signaling transduces shear stress--dependent vasodilation of coronary arterioles. Circ Res 1997; 80:320-6. [PMID: 9048651 DOI: 10.1161/01.res.80.3.320] [Citation(s) in RCA: 129] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A direct relationship exists between shear stress and endothelium-dependent NO-mediated vasodilation of blood vessels. The transduction of shear stress to the biochemical signals resulting in the production of NO is, however, unknown. We tested the hypothesis that integrin binding to Arg-Gly-Asp(RGD) peptide sequences in extracellular matrix proteins is a critical step in initiation of the signaling sequence whereby shear stress activates endothelial tyrosine kinase(s) and induces vasodilation of isolated arterioles. Isolated coronary arterioles were exposed to increasing shear stress under control conditions and in the presence of a synthetic peptide, GRGDNP, to competitively inhibit integrin binding to extracellular matrix proteins containing RGD peptide sequences. Intraluminal GRGDNP (0.1, 0.5, and 1.0 mmol/L) inhibited shear stress-induced vasodilation in a concentration-dependent manner. Application of GRGDNP had no effect on endothelium-dependent relaxation to substance P (10(-12) to 10(-8) mol/L). An inactive structural analogue, GRGESP, did not alter shear stress-induced vasodilation. To further elucidate the integrin involved in shear stress-induced vasodilation, we administered a blocking antibody to the integrin beta 3 chain (F11) and observed significant attenuation of the vasodilation. Shear stress was also associated with an increase in tyrosine kinase activity, as assessed by anti-phosphotyrosine binding. Application of GRGDNP significantly decreased anti-phosphotyrosine binding during shear stress, suggesting a link between tyrosine kinase activation and integrin signaling during this vasodilatory response. Taken together, these results indicate that integrin-matrix interactions, possibly at focal adhesions, are of cardinal importance in the signaling pathway of shear stress-induced vasodilation.
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Davis MJ, Rott P, Warmuth CJ, Chatenet M, Baudin P. Intraspecific Genomic Variation Within Xanthomonas albilineans, the Sugarcane Leaf Scald Pathogen. PHYTOPATHOLOGY 1997; 87:316-324. [PMID: 18945175 DOI: 10.1094/phyto.1997.87.3.316] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
ABSTRACT To better understand the nature of recent outbreaks of leaf scald disease of sugarcane in a number of sugarcane production regions of the world including Florida, Guadeloupe, Louisiana, Mauritius, Taiwan, and Texas, a study of the worldwide genetic variation of the pathogen was undertaken. A total of 218 strains from 31 geographic locations were examined. Genomic DNA of each strain was digested with the rare cutting restriction enzyme SpeI, and the fragments were separated by pulsed-field gel electrophoresis (PFGE). A total of 102 bands were identified, and 54 different DNA banding patterns (haplotypes) were observed. Eight groups of banding patterns, designated PFGE groups A through H, were consistently detected by visual, principal component, and cluster analyses. Five groups were comprised of multiple haplotypes representing numerous strains, and three were comprised of single haplotypes representing one strain each. The leaf scald outbreaks in Florida, Louisiana, Texas, and possibly Guadeloupe and Taiwan could be attributed to the introduction of strains belonging to PFGE group B. When infection by two strains each of the newly introduced strains (PFGE group B) and those previously present in Florida (PFGE group A) was analyzed in 22 sugarcane cultivars by reisolation 24 weeks after inoculation, a significantly greater mean frequency was detected for PFGE group B strains and no cultivar by PFGE group interaction was observed. Inadvertent dispersal of the pathogen among plants, possibly by means of aerosols or splashing water, was detected in a subsequent experiment. Strains of PFGE group B were recovered from the internal tissues of some plants inoculated with PFGE group A strains and were also found to be epiphytic colonizers of nonsymptomatic, noninoculated plants adjacent to the inoculated plants; whereas strains of PFGE group A were recovered only from plants that had been inoculated with them. Thus, the possibility became more apparent that strain variation might be associated, at least in part, with factors governing plant-to-plant spread of the pathogen in nature.
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Lett BT, Grant VL, Neville LL, Davis MJ, Koh MT. Chlordiazepoxide counteracts activity-induced suppression of eating in rats. Exp Clin Psychopharmacol 1997. [PMID: 9234036 DOI: 10.1037//1064-1297.5.1.24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Because benzodiazepines such as chlordiazepoxide increase food intake, the present experiments tested the effect of chlordiazepoxide on food intake in an animal model of anorexia nervosa, called activity anorexia (AA). To induce AA, rats (Rattus norvegicus) were maintained in activity wheels and restricted to a single 60-min feeding period each day. As previously found, this procedure suppressed food intake. After several days of this training, food intake was measured 30 min after the rats were injected with chlordiazepoxide (5 mg/kg) or saline. In 2 experiments, chlordiazepoxide counteracted the suppression of food intake produced by AA. Because benzodiazepines have been found to increase food intake in many mammalian species including primates, the present results suggest that benzodiazepines could be useful in the treatment of anorexia nervosa.
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80
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Callegari A, Srivastava HK, Merker U, Lehmann KK, Scoles G, Davis MJ. Eigenstate resolved infrared–infrared double-resonance study of intramolecular vibrational relaxation in benzene: First overtone of the CH stretch. J Chem Phys 1997. [DOI: 10.1063/1.473205] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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81
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Muller JM, Davis MJ, Chilian WM. Integrated regulation of pressure and flow in the coronary microcirculation. Cardiovasc Res 1996. [PMID: 8915185 DOI: 10.1016/s0008- 6363(96)00111-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
There are many mechanisms that contribute to the regulation of coronary blood flow including vasodilatory metabolites, myogenic regulation, flow- or shear stress-mediated vasodilation, and neurohumoral influences. It is interesting to note that coronary arterioles of varying sizes appear to possess different sensitivities to these regulatory factors, but each appears to dominate the control of a particular segment of the microvasculature. For example, during metabolic hyperemia the smallest arterioles seem to be most sensitive to the effects of metabolites, but metabolic and myogenic mechanisms that dictate the tone of upstream microvessels likely act in concert to facilitate the overall adjustments in coronary vasomotor tone. Neurohumoral mechanisms, seem to modulate the robustness of these intrinisic adjustments, perhaps by restraining the extent of vasodilation. The purpose of this review is to discuss these many regulatory mechanisms and also present a framework by which the vasoactive reactions elicited by these different mechanisms are integrated into coordinated responses of the entire coronary vascular network.
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82
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Davis MJ. Outcomes and accountability. Can dentistry prove the benefits of care? THE NEW YORK STATE DENTAL JOURNAL 1996; 62:42-6. [PMID: 8973104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
As managed care increases in influence, dentists must be prepared to document the efficacy of all treatment modalities in order to maintain control over the care their patients receive. We, rather than third parties, are ultimately accountable for the results of the care we provide. The outcomes assessment process can yield essential, clear evidence of the efficacy, cost-effectiveness and benefits of the care we provide to patients.
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83
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Muller JM, Davis MJ, Chilian WM. Integrated regulation of pressure and flow in the coronary microcirculation. Cardiovasc Res 1996; 32:668-78. [PMID: 8915185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
There are many mechanisms that contribute to the regulation of coronary blood flow including vasodilatory metabolites, myogenic regulation, flow- or shear stress-mediated vasodilation, and neurohumoral influences. It is interesting to note that coronary arterioles of varying sizes appear to possess different sensitivities to these regulatory factors, but each appears to dominate the control of a particular segment of the microvasculature. For example, during metabolic hyperemia the smallest arterioles seem to be most sensitive to the effects of metabolites, but metabolic and myogenic mechanisms that dictate the tone of upstream microvessels likely act in concert to facilitate the overall adjustments in coronary vasomotor tone. Neurohumoral mechanisms, seem to modulate the robustness of these intrinisic adjustments, perhaps by restraining the extent of vasodilation. The purpose of this review is to discuss these many regulatory mechanisms and also present a framework by which the vasoactive reactions elicited by these different mechanisms are integrated into coordinated responses of the entire coronary vascular network.
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84
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Davis MJ, Coote PJ, O'Byrne CP. Acid tolerance in Listeria monocytogenes: the adaptive acid tolerance response (ATR) and growth-phase-dependent acid resistance. MICROBIOLOGY (READING, ENGLAND) 1996; 142 ( Pt 10):2975-82. [PMID: 8885415 DOI: 10.1099/13500872-142-10-2975] [Citation(s) in RCA: 187] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Listeria monocytogenes acquired increased acid tolerance during exponential growth upon exposure to sublethal acid stress, a response designated the acid tolerance response (ATR). Maximal acid resistance was seen when the organism was exposed to pH 5.0 for 1 h prior to challenge at pH 3.0, although intermediate levels of protection were afforded by exposure to pH values ranging from 4.0 to 6.0. A 60 min adaptive period was required for the development of maximal acid tolerance; during this period the level of acid tolerance increased gradually. Full expression of the ATR required de novo protein synthesis; chloramphenicol, a protein synthesis inhibitor, prevented full induction of acid tolerance. Analysis of protein expression during the adaptive period by two-dimensional gel electrophoresis revealed a change in the expression of at least 23 proteins compared to the non-adapted culture. Eleven proteins showed induced expression while 12 were repressed, implying that the ATR is a complex response involving a modulation in the expression of a large number of genes. In addition to the exponential phase ATR, L.monocytogenes also developed increased acid resistance upon entry into the stationary phase; this response appeared to be independent of the pH-dependent ATR seen during exponential growth.
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85
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Muller JM, Davis MJ, Chilian WM. Integrated regulation of pressure and flow in the coronary microcirculation. Cardiovasc Res 1996. [DOI: 10.1016/s0008-6363(96)00111-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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86
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Rott PC, Costet L, Davis MJ, Frutos R, Gabriel DW. At least two separate gene clusters are involved in albicidin production by Xanthomonas albilineans. J Bacteriol 1996; 178:4590-6. [PMID: 8755889 PMCID: PMC178228 DOI: 10.1128/jb.178.15.4590-4596.1996] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Transposon mutagenesis was used to obtain mutations affecting production of the toxin albicidin in Xanthomonas albilineans, which causes leaf scald disease of sugarcane and is also pathogenic to corn. Transposon Tn5-gusA inserted randomly into genomic DNA of X. albilineans Xa23R1 at a frequency of 10(-4) to 10(-5) per recipient after conjugal transfer from Escherichia coli. Fifty prototrophic mutants defective in albicidin production were isolated from 7,100 Tn5-gusA insertional derivatives tested for toxin production by an antibiosis bioassay. EcoRI fragments containing Tn5 flanking sequences from two mutants (AM15 and AM40) were cloned and used to probe a wild-type Xa23R1 DNA library by colony hybridization. Nine cosmids showed homology to the AM15 probe, and six showed homology to the AM40 probe. Four cosmid clones hybridized to both probes. Forty-five of the 50 defective mutants were restored to albicidin production with two overlapping cosmid clones. Restriction mapping showed that these mutants span a genomic region of about 48 kb. At least one other gene cluster is also involved in albicidin production in Xa23R1. DNA fragments from the 48-kb cluster proved to be very specific to X. albilineans. Some mutants affected in albicidin production retain their ability to colonize sugarcane cultivated in vitro.
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87
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Jones CJ, Kuo L, Davis MJ, Chilian WM. In vivo and in vitro vasoactive reactions of coronary arteriolar microvessels to nitroglycerin. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 271:H461-8. [PMID: 8770085 DOI: 10.1152/ajpheart.1996.271.2.h461] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The actions of nitroglycerin on the coronary microcirculation are controversial, with some laboratories reporting that coronary arterioles dilate to the drug and others reporting that they do not. Our goal was to reconcile these disparate observations. Specifically, we hypothesized that dilation of coronary arterioles by nitroglycerin is overwhelmed by intrinsic autoregulatory escape mechanisms. Accordingly, we projected that coronary arterioles would show transient, but not sustained, dilation to nitroglycerin in vivo. Furthermore, we hypothesized that isolated coronary arterioles would show sustained dilation to the drug, because intrinsic escape mechanisms would be absent under these conditions. To test these hypotheses, we measured diameter changes of canine coronary microvessels in vivo during continuous nitroglycerin administration (intracoronary infusion or epicardial suffusion) using intravital fluorescent microscopy (n = 17 dogs) at two time points: early (1-3 min), when coronary artery blood flow velocity was increased, and late (15-20 min), after blood flow velocity returned to control. Tb study responses of coronary arterioles in the absence of autoregulatory influences, we measured the diameter of isolated canine coronary arterioles to varying doses of nitroglycerin (n = 8 vessels, maximal diameter 81 +/- 4 microns). During the early phase of nitroglycerin infusion (1,3, and 10 micrograms.kg-1.min-1), coronary arterioles dilated by 4 +/- 1, 7 +/- 2, and 13 +/- 2% (all P < 0.05), whereas small arteries dilated by 1 +/- 2, 3 +/- 1, and 4 +/- 1%, respectively (P < 0.05 for the higher doses). Coronary artery blood velocity measured increased by 45 +/- 15% (3 micrograms.kg-1.min-1, P < 0.05). Suffusion of nitroglycerin (10(-5) M) dilated coronary arterioles, but not small arteries, by 17 +/- 5% (P < 0.05) between 1 and 3 min. After 15-20 min of nitroglycerin (3 micrograms.kg-1.min-1 by intracoronary infusion), diameters of coronary arterioles and coronary artery blood velocity returned to control, whereas dilation of small arteries remained significant at 4 +/- 1%. Coronary arteriolar dilation by epicardial suffusion of nitroglycerin also waned to control values by 15-20 min, whereas dilation of small arteries was observed: 5 +/- 2% (P < 0.05). In vitro, nitroglycerin caused dose-dependent dilation of coronary arterioles to their maximal diameter, which was sustained for 20 min. Thus nitroglycerin dilates coronary arterioles and small arteries. The dilation in vivo is transient for arterioles but sustained for arteries. In vitro, the dilation is sustained. Because microvessels in vitro are capable of sustaining dilation for 20 min, we conclude that the waning of arteriolar dilation in vivo is related to autoregulatory escape from dilation by nitroglycerin.
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Davis MJ, Woolf AD. Role of antimalarials in rheumatoid arthritis – the British experience. Lupus 1996. [DOI: 10.1177/0961203396005001091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Antimalarials have been used to treat rheumatoid arthritis (RA) for over 40 years, the first report of suggestive efficacy being published in 1951. Over the years they have become part of the established treatment of RA being one of a category of drugs referred to as disease modifying anti-rheumatic drugs (DMARDs). The onset of action with antimalarials is slow. Most patients use these drugs in combination with non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics. This article reviews the evidence for the efficacy of antimalarials, their place in comparison to other DMARDs and comments on the current use in RA as perceived in British rheumatology.
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Davis MJ, Woolf AD. Role of antimalarials in rheumatoid arthritis--the British experience. Lupus 1996; 5 Suppl 1:S37-40. [PMID: 8803909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Antimalarials have been used to treat rheumatoid arthritis (RA) for over 40 years, the first report of suggestive efficacy being published in 1951. Over the years they have become part of the established treatment of RA being one of a category of drugs referred to as disease modifying anti-rheumatic drugs (DMARDs). The onset of action with antimalarials is slow. Most patients use these drugs in combination with non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics. This article reviews the evidence for the efficacy of antimalarials, their place in comparison to other DMARDs and comments on the current use in RA as perceived in British rheumatology.
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90
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Muller JM, Davis MJ, Chilian WM. Coronary arteriolar flow-induced vasodilation signals through tyrosine kinase. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:H1878-84. [PMID: 8764235 DOI: 10.1152/ajpheart.1996.270.6.h1878] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Coronary arterioles demonstrate flow-dependent vasodilation that is mediated by endothelial release of nitric oxide. The signaling mechanisms for this response remain unknown. Because tyrosine kinases are an enzyme family linked to many signaling pathways, including some for mechanosensitive transduction, we hypothesized that tyrosine kinase activation is a critical step in flow-induced vasodilation. To test this hypothesis, coronary arterioles were isolated, cannulated with micropipettes, and perfused by two independent reservoir systems. Intraluminal pressure was set at 60 cmH2O, and flow was generated by changing the heights of the reservoirs in equal and opposite directions, thus establishing a pressure difference across the arteriole without altering intraluminal pressure. Vasodilatory responses to intraluminal flow and substance P (1 x 10(-12) to 1 x 10(-7) M) were evaluated before and after intraluminal application of the tyrosine kinase inhibitors genistein (5 microM) and piceatannol (10 microM). Exposure to these inhibitors did not alter spontaneous tone. Substance P caused dose-dependent vasodilation that was not affected by genistein or piceatannol. Increases in intraluminal flow (generated by pressure differences ranging from 4 to 60 cmH2O) elicited graded increases in diameter. Both genistein and piceatannol inhibited the vasodilatory responses to flow. Treatment with daidzein, an inactive analogue of genistein, had no effect on either the flow-induced responses or substance P-induced vasodilation. To further confirm that tyrosine kinase activation is involved in flow-induced vasodilation, vessels were exposed to flow in the absence or presence of genistein and subsequently stained with a fluorescein isothiocyanate-labeled phosphotyrosine antibody. Exposure to flow significantly increased fluorescence of endothelial cells. Genistein treatment reversed the flow-induced increase in tyrosine phosphorylation. These results indicate that endothelium-dependent, flow-induced vasodilation in isolated porcine coronary arterioles is accompanied by an increase in tyrosine kinase activity. We conclude that endothelium-dependent, nitroxidergic, flow-induced vasodilation is mediated, at least in part, by a signaling pathway involving a tyrosine kinase.
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Weerasooriya HR, Harris AH, Davis MJ. Cost effectiveness of day stay versus inpatient radiofrequency (RF) ablation for the treatment of supraventricular tachyarrhythmias. AUSTRALIAN AND NEW ZEALAND JOURNAL OF MEDICINE 1996; 26:206-9. [PMID: 8744619 DOI: 10.1111/j.1445-5994.1996.tb00885.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND It is well established that radiofrequency (RF) ablation is the most cost effective treatment strategy for patients with supraventricular tachycardia. Previous cost estimates assumed at least an overnight stay following RF ablation. Day stay RF ablation however appears to be a safe alternative. AIMS The aim of this study was to compare day stay and inpatient catheter ablation in terms of cost, efficacy and safety. METHODS This was a retrospective cost effectiveness analysis. The study population consisted of 25 consecutive patients who underwent day stay RF ablation and 25 consecutive patients who underwent inpatient RF ablation (historical controls). Economic analysis was based upon a detailed clinical costing. RESULTS The mean overall cost per patient of inpatient RF ablation in 1994 Australian dollar values is $2354 (SD, $642) compared with $1876 (SD, $595) for day stay RF ablation (p < 0.01). Day stay RF ablation is a cost effective alternative to inpatient RF ablation.
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92
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Hill MA, Davis MJ, Song J, Zou H. Calcium dependence of indolactam-mediated contractions in resistance vessels. J Pharmacol Exp Ther 1996; 276:867-74. [PMID: 8786563] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The protein kinase C activator, (-)-indolactam, has been shown to enhance reactivity of arterioles by a mechanism not requiring an increase in intracellular Ca++ (Ca++i). The aim of this study was to characterize the Ca++ requirement for indolactam-induced contraction of resistance vessels. Studies were performed in small mesenteric arteries (diameter, 260 +/- microm), using intact segments or after permeabilization with alpha-toxin (500 U/ml). Additional studies were preformed using isolated smooth muscle cells to allow electrophysiological assessment of the effect of indolactam on voltage-gated Ca++ entry. Intact and permeabilized vessel segments showed dose-dependent constriction to indolactam. Studies of Fura 2-loaded vessels and permeabilized segments maintained at low Ca++i, showed that the constriction occurred without an overt increase in Ca++i. That Ca++ was required was evident by near maximal relaxation after the removal of Ca++. Patch clamp studies indicated that indolactam potentiated voltage-gated Ca++ entry; however, nifedipine (0.5 microM) and La (0.2 or 1 mM) were relatively ineffective in reversing the contraction, indicating that voltage-gated Ca++ entry was not an absolute requirement. In intact vessel segments, the myosin light chain (MLC) kinase inhibitors, ML-7 and ML-9, reversed the indolactam contraction, suggesting the requirement of the MLC chain phosphorylation pathway. Furthermore, indolactam caused by a significant increase in MLC phosphorylation in permeabilized vessels, despite clamping of Ca++i at pCa 7.0. The data are consistent with the suggestion that the protein kinase C activator, indolactam, acts to modulate the Ca++ sensitivity of the smooth muscle contractile process such that higher than expected levels of MLC phosphorylation exist for a given level of Ca++i.
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93
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Davis MJ, Vogel LD. Local anesthetic safety in pediatric patients. THE NEW YORK STATE DENTAL JOURNAL 1996; 62:32-5. [PMID: 8850195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Local anesthetic, when administered properly and in correct dosages, is an essential part of pediatric oral health care. Recent adjustments to maximum safe dosage and careful administration techniques make local anesthetic use with children even safer and more effective. Safe dosage levels, technique recommendations and early clinical signs of possible overdose are presented here.
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95
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Sharma NR, Davis MJ. Calcium entry activated by store depletion in coronary endothelium is promoted by tyrosine phosphorylation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1996; 270:H267-74. [PMID: 8769761 DOI: 10.1152/ajpheart.1996.270.1.h267] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Application of substance P (SP), a potent endothelium-dependent vasodilator, to porcine coronary artery endothelial cells (PCAECs) results in release of Ca2+ from intracellular stores followed by extracellular Ca2+ influx. We tested the hypothesis that intracellular store depletion results in tyrosine phosphorylation, which promotes Ca2+ influx. PCAECs labeled with antiphosphotyrosine antibody conjugated to fluorescein isothiocyanate showed a 3.3- to 3.4-fold increase in fluorescence in response to SP or 2,5-di-tert-butylhydroquinone (BHQ), an agent that depletes intracellular stores by inhibiting the endoplasmic reticulum Ca(2+)-adenosinetriphosphatase. In both cases, the tyrosine kinase inhibitor, genistein, reduced the fluorescence intensity to near-basal levels. Pretreatment of PCAECs with the tyrosine kinase inhibitors, genistein or tyrphostin, induced a significant reduction in the plateau phase of SP-induced Ca2+ elevation with no effect on the release of Ca2+ from stores. Neither daidzein, a structurally similar but inactive analogue of genistein, nor H-7, a serine-threonine kinase inhibitor, affected SP-induced Ca2+ influx. Voltage-clamp recordings using the perforated patch technique with simultaneous Ca2+ measurements showed that intracellular Ca2+ elevation and inward current activated by SP and BHQ were reduced by 60-70% in response to genistein. These data indicate that the link between store depletion and Ca2+ influx in endothelial cells requires tyrosine phosphorylation.
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96
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Rankin JM, Davis MJ. Protrusion of retention wire from Encor-Dec passive fixation atrial pacing lead. Lancet 1995; 346:1169-70. [PMID: 7475643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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97
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Deodhar AA, Brabyn J, Jones PW, Davis MJ, Woolf AD. Longitudinal study of hand bone densitometry in rheumatoid arthritis. ARTHRITIS AND RHEUMATISM 1995; 38:1204-10. [PMID: 7575713 DOI: 10.1002/art.1780380905] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
OBJECTIVE To measure hand bone mineral content (BMC) by dual x-ray absorptiometry and to seek clinical correlates in patients with rheumatoid arthritis (RA), in a prospective, longitudinal study. METHODS Eighty-one patients with non-steroid-treated RA were assessed at baseline and at month 12, for hand BMC and for disease activity and severity. Hand BMC in patients was compared with that in a control group of 95 normal volunteers, and rate of loss was compared with that in 37 controls. RESULTS At the initial assessment, male and female patients with RA had lower hand BMC than controls, after correction for age, height, and weight (mean reduction 7.5% in men [P = 0.003] and 7.8% in women [P = 0.01]). After 1 year, there was a further loss of hand BMC in patients (median loss 3.25% in men [P = 0.001] and 1.46% in women [P = 0.05]), but normal controls did not have significant changes in their hand BMC. In patients with disease duration of < 2 years at study entry, the parameters of disease activity improved over 1 year, but they lost significant amounts of hand BMC. Hand BMC loss correlated with baseline C-reactive protein levels. In those with RA of > 2 years duration at entry, the Health Assessment Questionnaire scores and Larsen scores had worsened after 1 year, but there was no significant loss of hand BMC. CONCLUSION Patients with RA had low hand BMC compared with normal controls, even within 2 years of disease onset. The rate of loss was highest in patients with early disease and correlated with measures of initial disease activity. This loss continued despite clinical improvement.
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Kuo L, Davis MJ, Chilian WM. Longitudinal gradients for endothelium-dependent and -independent vascular responses in the coronary microcirculation. Circulation 1995; 92:518-25. [PMID: 7543382 DOI: 10.1161/01.cir.92.3.518] [Citation(s) in RCA: 181] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Coronary microvessels (< 300 microns in diameter) have been demonstrated to be important in the regulation of local resistance and flow. Recent studies also suggest that these microvessels are more responsive to physiological and pharmacological stimuli than conduit vessels. However, little is known regarding the relative sensitivity of different microvascular segments in response to flow (shear stress) and agonists. The goal of this study was to test the hypothesis that a longitudinal gradient for shear stress- and agonist-induced dilation exists in the coronary microcirculation. METHODS AND RESULTS Experiments were performed in four different sizes of porcine subepicardial coronary arterial microvessels: small arterioles (40 +/- 1-micron ID with resting tone); intermediate arterioles (60 +/- 1 micron); large arterioles (106 +/- 4 micron); and small arteries (179 +/- 9 microns). Vessels were isolated and cannulated to allow luminal pressure and flow to be independently controlled. All vessels developed active tone (to approximately 65% to 75% of maximum diameter) at their control luminal pressures and showed graded dilations to stepwise increases in shear stress (0 to 10 dynes/cm2). For arterioles, the magnitude of the dilations increased as vessel size increased. The highest shear stress produced 21 +/- 3%, 32 +/- 2%, and 52 +/- 5% increases in diameter in small, intermediate, and large arterioles, respectively. Small arteries dilated only 22 +/- 6%. The endothelium-dependent vasodilator substance P (SP) produced dose-dependent dilation of all vessels with a threshold at 10(-16) mol/L. Arterioles were maximally dilated at 10(-9) mol/L SP. However, this dose produced only 80% dilation in small arteries. The ED50 for SP was shifted to the right by two orders of magnitude in small arteries compared with the arterioles. Adenosine preferentially dilated small arterioles, and the dose-response curves shifted to the right for larger vessels. The thresholds for adenosine-induced dilation were 10(-12), 10(-11), and 10(-9) mol/L for small, intermediate, and large arterioles, respectively. The endothelium-independent vasodilator nitroprusside produced identical dose-dependent dilations in all vessel segments. CONCLUSIONS The results indicate that the pig coronary circulation exhibits a heterogeneity in physiological and pharmacological responses along the microvascular network. Small arterioles are more sensitive to adenosine, but large arterioles are more responsive to shear-stress stimulation. We speculate that site-specific preferential responses may play a crucial role in coordinating overall vascular function in the coronary microvascular network.
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Davis MJ. Orofacial trauma management. Patient assessment and documentation. THE NEW YORK STATE DENTAL JOURNAL 1995; 61:42-6. [PMID: 7566827] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
New technologies and treatments for managing children with orofacial trauma are constantly updated and available to the practitioner through current literature. What often fails to be appreciated, however, is that orofacial injury is a subset of head trauma and may have systemic emergent considerations that supersede the oral conditions being addressed. The complexity of a thorough assessment of the child from both medical and dental standpoints requires a systematic approach, which in turn can be guided by an appropriate document for inclusion in the chart. Further, such a document will serve as an important record should future civil litigation ensure from the traumatic incident.
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May CD, Smith PR, Murdock CJ, Davis MJ. The impact of the implantable cardioverter defibrillator on quality-of-life. Pacing Clin Electrophysiol 1995; 18:1411-8. [PMID: 7567594 DOI: 10.1111/j.1540-8159.1995.tb02603.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The implantable cardioverter defibrillator (ICD) is an established treatment for patients with life-threatening ventricular arrhythmias. While it clearly reduces the incidence of death from recurrent arrhythmia, little is known about the impact on patients' quality-of-life. In this prospective study, quality-of-life was assessed by questionnaire before and after ICD implantation. The "Sickness Impact Profile" (SIP), which evaluates physical, psychosocial, and other activities, as well as functions of daily life, was used. Employment and rehospitalization rates were also examined. Twenty-one of 23 consecutive patients, aged 58 +/- 11 years, undergoing ICD implantation at Royal Perth Hospital were studied. During the 14 +/- 8 month follow-up, 4 patients died. Functional capacity was unchanged in all but one of the survivors in whom it improved from New York Heart Association Class III to II. Four of 8 survivors employed before implant have since retired. Six patients required rehospitalization on 13 occasions, problems related to arrhythmias or the ICD. Overall SIP scores preimplant (11.2 +/- 9.3; P < 0.05) were significantly worse at 6-month follow-up (21.7 +/- 18.2), but returned to preimplant levels by 12-month follow-up (8.8 +/- 10.8; NS). This was primarily due to transient problems in the areas of emotional behavior, alertness, and social interaction. SIP psychosocial dimension scores: preimplant: 7.2 +/- 9.0; 6-month: 17.8 +/- 18.1 (P < 0.05); and 12-month: 8.6 +/- 10.3 (NS). Early retirement and hospitalizations due to arrhythmias may still be expected even after implantation of an ICD; however, quality-of-life appears only to temporarily decline.
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