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Biomedical subjects

A Bishop

Publications and source records attributed to A Bishop.

At least 37 records · Page 2Linked to original sources
PubMed1998

Erosive oesophagitis: outcome of repeated long term maintenance treatment with low dose omeprazole 10 mg or placebo.

AIMS: To investigate the efficacy of daily maintenance treatment with omeprazole 10 mg in reducing the relapse rate of healed erosive oesophagitis. METHODS: Three hundred patients with erosive oesophagitis (grade 2 or greater) received omeprazole 20 mg daily for 12 weeks, followed by 40 mg daily for a further 12 weeks if required. After healing, patients were randomised to double blind treatment with omeprazole 10 mg daily or placebo for up to 18 months. On relapse the treatment cycle was repeated. RESULTS: The cumulative healing rate at 12 weeks in the initial healing period was 95%, and 96% and 98% on rehealing courses after relapse in the first and second maintenance periods respectively. After 12 weeks of treatment, 98% of patients were free from heartburn and 97% were free of all reflux related symptoms. Relapse in the subgroup of patients who relapsed in both maintenance periods was infrequent on omeprazole 20 mg daily: only 9% at two years. Gastrin concentrations rose above normal in one third of patients. One patient had linear hyperplasia of endocrine cells and another had micronodular hyperplasia. There were no side effects definitely attributable to omeprazole. CONCLUSION: Maintenance treatment with omeprazole 10 mg daily keeps about 60% of patients with erosive oesophagitis in prolonged remission. Patients relapsing once are likely to do so again; they can subsequently be treated effectively with omeprazole 20 mg daily.

Anti-Ulcer Agents↗
PubMed1997

Increased airway pressure and simulated branch pulmonary artery stenosis increase pulmonary regurgitation after repair of tetralogy of Fallot. Real-time analysis with a conductance catheter technique.

BACKGROUND: Pulmonary regurgitation (PR) is an important determinant of outcome after repair of tetralogy of Fallot. Baseline PR was measured by magnetic resonance (MR) phase velocity mapping and from real-time right ventricular pressure-volume loops with a conductance catheter. Subsequently, the impact of two loading maneuvers (increased airway pressure, simulated branch pulmonary artery stenosis) on PR was assessed by the conductance catheter method. METHODS AND RESULTS: Thirteen patients, 3 to 35 years after tetralogy of Fallot repair or pulmonary valvotomy, had PR measured by MR phase velocity mapping while breathing spontaneously. During catheterization under general anesthesia. PR was estimated from right ventricular pressure-volume loops generated by conductance and microtip pressure catheters. The effect of increased airway pressure (continuous positive airway pressure, 20 cm H2O; n = 12) and simulated branch pulmonary artery stenosis (transient balloon occlusion of a branch pulmonary artery, n = 7) was measured. Basal PR fraction derived by MR and from right ventricular pressure-volume loops had a correlation coefficient of .76 and mean of differences of 2.0 +/- 18.2% (95% limits of agreement). Increased airway pressure increased PR (16.3 +/- 11.4% to 25.7 +/- 17.3%, P < .01). Simulated branch pulmonary artery stenosis increased right ventricular end-systolic pressure (69.1 +/- 21.4 to 78.7 +/- 23.1 mm Hg, P < .05) and PR (27.5 +/- 11.3% to 36.9 +/- 12.8%, P < .05). CONCLUSIONS: There was reasonable agreement between MR phase velocity-derived PR fraction and that obtained from right ventricular pressure-volume loops generated by use of conductance and pressure-microtip catheters. Exacerbation of PR by increased airway pressure and branch pulmonary stenosis may be relevant to the acute postoperative and long-term management, respectively, of patients after repair of tetralogy of Fallot.

Adolescent↗
PubMed1997

Resting right ventricular function in patients with coronary artery disease: pressure volume analysis using conductance catheters.

Right ventricular pressure volume cycles from patients with coronary artery disease were created in order to assess their characteristics and the effects of peak ventricular pressure and right and left artery coronary disease. Thirty-three patients undergoing diagnostic catheterisation for ischaemic heart disease underwent right ventricular catheterisation with a micromanometer and a conductance catheter. Simultaneous pressure and volume signals were recorded and analysed as functions of time, and of each other, forming pressure volume cycles. A total of 19/33 (58%) patients had an abnormal pressure volume loop with a clear end systolic shoulder, and an isovolumic relaxation phase. The mean peak ventricular pressure for all patients was raised (35.2 S.D. 11.8 mmHg), but there was no correlation between indices of shape and peak systolic pressure. Values of dP/dtmax were also raised, but there was no significant difference in this or any other index between patients with left or right coronary artery disease. Thus, in patients with coronary artery disease, the right ventricular pressure volume loop is frequently abnormal in a pattern that is recognised as a feature of an increased ventricular afterload.

Angina Pectoris↗
PubMed1997

Clinical application of the conductance catheter technique in the adult human right ventricle.

This study examines the use of conductance catheters to assess human right ventricular volume. Ten patients undergoing diagnostic cardiac catheterisation underwent right heart catheterisation with a conductance catheter and micromanometer, and a thermodilution catheter before and after fluid loading. Parallel wall conductance (Vc), and the multiplication factor relating conductance and thermodilution derived stroke volumes (å) were derived at each steady state. Pressure-volume cycles were analyzed at steady state and during fluid loading. Fluid loading resulted in a significant increase in cardiac output, and change in maximum and minimum cycle volume. There was no significant change in å (mean 0.40 S.D. 0.20) or Vc (mean 126.4 S.D. 59.6 ml) at higher cardiac outputs or ventricular volumes. Right ventricular pressure-volume cycles were formed demonstrating characteristic lack of clear isovolumic contraction and relaxation phases, and low cycle efficiencies (mean 0.62 S.D. 0.16). Serial cycles recorded during volume loading defined an end systolic pressure-volume relation more reliably than a stroke work end diastolic volume relation. Thus, a conductance derived volume signal can be obtained in the human right ventricle which can be interpreted as a continuous and instantaneous index of right ventricular volume, allowing the construction of real time pressure-volume cycles.

Adult↗
PubMed1997

Right ventricular dysfunction during coronary artery occlusion: pressure-volume analysis using conductance catheters during coronary angioplasty.

OBJECTIVE: To study the effects of coronary artery occlusion on the pressure-volume relations of the right ventricle. DESIGN: Right ventricular pressure-volume cycles were studied using conductance catheters and micromanometers in 19 subjects undergoing coronary angioplasty in a tertiary referral cardiac centre. RESULTS: Catheter occlusions of either the left anterior descending coronary artery or the right coronary artery were associated with a decline in stroke work (mean change (SD): left-13.3 (15.8)%, p = 0.008; right -13.5(16.5)%, p = 0.04). Two patterns of change were evident: an upward shift usually associated with occlusion in the left coronary artery, and a rightward shift in the right coronary artery. In the former there was an increase in maximum ventricular volume (mean change: 3.0(2.7)%, p = 0.004) and in minimum ventricular volume (mean change: 2.3(2.7)%, p = 0.01) and a fall in peak pressure (mean change: -4.8 (5.1)%, p = 0.04). In the latter there was an increase in peak pressure (mean change 9.9(16.3)%, p = 0.04) and an increase in minimum ventricular volume (mean change 3.7(5.0)%, p = 0.02) leading to a fall in stroke volume (mean change -13.3(15.8)%, p = 0.008). CONCLUSIONS: Occlusion of the left anterior descending coronary artery or the right coronary artery is associated with a decline in right ventricular work. However, different patterns of change in indices of preload and afterload lead to different effects on overall right ventricular pump function.

Angioplasty, Balloon, Coronary↗
PubMed1997

Histamine H2 receptor antagonist-refractory oesophagitis: the efficacy of long-term omeprazole maintenance treatment.

BACKGROUND: Erosive oesophagitis refractory to high dose histamine H2 receptor antagonists (definition: failure to heal fully after > or = 3 months' treatment with cimetidine 3.2 g or ranitidine 0.9 g) responds well to omeprazole 40 mg daily but frequently relapses when the patients are put back on maintenance H2 receptor antagonists at medium or even high dose (e.g. cimetidine 1.6 g and 3.2 g, respectively). AIM: To investigate the efficacy of maintenance omeprazole 20 mg daily in refractory erosive oesophagitis. PATIENTS & METHODS: In this open, sequential study, patients with H2 receptor antagonist-refractory oesophagitis were healed on omeprazole 40 mg daily and then put on maintenance H2 receptor antagonists (cimetidine 1.6 g or 3.2 g). Relapses were re-treated with omeprazole 40 mg; upon rehealing, patients were put on maintenance omeprazole 20 mg daily for up to 4.5 years. RESULTS: Healing on omeprazole occurred in 38 out of 39 patients (97%) at 12 weeks. Only six of the 38 patients (16%) relapsed (asymptomatic in half) during subsequent maintenance treatment, whereas all had relapsed earlier on high dose H2 receptor antagonists. CONCLUSION: Within the limits of interpretation of an open study, omeprazole 20 mg daily seems effective in maintaining prolonged remission in this group of patients with H2 receptor antagonist-refractory oesophagitis.

Adult↗
PubMed1996

Production of [18F]F2 using the 16O(3He,p)18F reaction.

For the first time, the 16O(3He,p)18F reaction has been used for the production of 18F electrophilic reagents. The predominant reactive chemical specie recovered in the single-step postirradiation gases was [18F]F2. Decay curve and Ge(Li) analyses established the main radionuclidic impurities in this nuclear reaction as 11C and 15O. Recovery of the 18F activity was exceptionally high, approaching 90% using an electroformed nickel target body. Consistent 18F recoveries for this nuclear reaction (approximately 70%) were realized with a novel aluminum target body. The utility of the [18F]F2 recovered from this oxygen gas target system in radiopharmaceutical preparations is demonstrated by the successful synthesis of 6-[18F]fluoro-L-dopa (11.0 mCi at EOB) via a fluorodemercuration method.

Fluorine Radioisotopes↗
PubMed1996

Proton irradiation of [18O]O2: production of [18F]F2 and [18F]F2 + [18F] OF2.

The production of 18F electrophilic reagents via the 18O(p,n)18F reaction has been investigated in small-volume target bodies made of aluminum, copper, gold-plated copper and nickel, having straight or conical bore shapes. Three irradiation protocols-single-step, two-step and modified two-step-were used for the recovery of the 18F activity. The single-step irradiation protocol was tested in all the target bodies. Based on the single-step performance, aluminum targets were utilized extensively in the investigation of the two-step and modified two-step irradiation protocols. With an 11-MeV cyclotron and using the two-step irradiation protocol, > 1Ci [18F]F2 was recovered reproducibly from an aluminum target body. Probable radical mechanisms for the formation of OF2 and FONO2 (fluorine nitrate) in the single-step and modified two-step targets are proposed based on the amount of ozone generated and the nitrogen impurity present in the target gases, respectively.

Aluminum↗
PubMed1996

Metals suitable for fluorine gas target bodies: first use of aluminum for the production of [18F]F2.

A comprehensive evaluation of different metals (aluminum, silver, copper, nickel, and gold-plated copper) was undertaken for the fabrication of target bodies with straight and conical bore shapes for the production of [18F]F2 via the 20Ne(d,alpha)18F nuclear reaction. Of these metals, aluminum, silver and copper have never been used for the production of [18F]F2. All these target bodies were easily passivated using a mild beam-induced plasma technique in the presence of 1% F2 in neon or argon. The recovery of 18F activity was higher with electroformed nickel and silver bodies, probably due to favorable thermal conductivities. Aluminum proved to be a useful material for fluorine gas targets. The consistent recovery of 18F activities, ease and low cost of manufacturing and low nuclear activation properties all make aluminum an ideal choice for fluorine gas targetry. To our knowledge, this investigation is the first to highlight the use of aluminum as a target body material for the routine production of [18F]F2. A reasonable mechanism based on the Langmuir-Rideal surface atom recombination is also proposed for the behavior of [18F]F2 recovery from a nickel target body.

Aluminum↗
PubMed1996

Identification and quantitation of gaseous compounds of fluorine generated in [18F]F2 target systems.

The first direct evidence for the chemical identity of the electrophilic fluorinating agents generated in 20Ne(d, alpha)18F (single-step), 18O(p,n)18F (single-step and two-step) and 16O(3He2+, p)18F (single-step) gas target systems, utilizing aluminum, silver, copper, nickel and gold plated copper target bodies, has been established with multinuclear NMR and mass spectral techniques. The major components of the reactive fraction from these targets were also quantitated using 19F NMR. Fluorine-19 NMR data of the reactive fraction of all proton and 3He2+ irradiated oxygen gas target systems showed the presence of oxygen difluoride in various proportions. Samples from the single-step method contained up to 20% OF2 while those from the two-step process had 0-5%. Fluorine nitrate (FONO2) was observed only as a minor component (0-3%) in the reactive fraction. The presence of OF2 and FONO2 was further confirmed by 17O and 15N NMR, respectively, using [17O]O2 and [15N]N2 spiked oxygen gas targets. The NMR results were supported by mass spectral data collected with a residual gas analyzer (RGA). Both 19F NMR and mass spectroscopy showed CF4 as the only major inert component in the single-step oxygen target products. As expected, the 19F NMR and mass spectral data showed that the reactive fraction of the neon gas target constituted only F2 and the inert fraction comprised of CF4 and NF3.

Fluorine Compounds↗
PubMed1996

Chemical reactivity of the 18F electrophilic reagents from the 18O(p,n) 18F gas target systems.

A comprehensive evaluation of the reactivity of 18F electrophilic fluorinating agents derived from the 18O(p,n)18F reaction conducted in target bodies made of aluminum, silver, copper, nickel, and gold-plated copper is reported. Two representative electrophilic reactions, namely addition across a double bond and substitution on an aromatic ring (fluorodemercuration and fluorodestannylation), were tested with the 18F activity generated in the [18O]O2 target systems. Identical reactions were also conducted with analogous nonradioactive fluorinating agents as control experiments. The products of all these reactions were analyzed by NMR spectroscopy. Results of these experiments clearly showed that 18F activities recovered from aluminum, silver, and copper target bodies were better suited for radiochemical syntheses, irrespective of the irradiation protocols employed. The 18F activity from a gold-plated target was suitable only for addition reactions. Further, the fluorodemercuration reaction essentially failed with the single-step irradiation technique conducted in nickel and gold-plated targets. In contrast, the fluorodestannylation reaction was quite successful with the 18F reagents recovered from all the target bodies and irradiation protocols.

Aluminum↗
PubMed1996

Deficient cellular cyclic AMP may cause both cardiac and skeletal muscle dysfunction in heart failure.

Deficient myocardial cyclic AMP concentrations contribute to abnormal Ca2+ handling and systolic and diastolic dysfunction in chronic heart failure (CHF). We tested the hypothesis that decreased cyclic AMP in skeletal muscle of animals with failure may contribute to the weakness and easy fatiguability also common in patients with CHF. We compared intracellular Ca2+ signaling and contractility in skeletal muscle preparations from rats 6 weeks after myocardial infarction-induced CHF versus sham-operated controls. Bundles of 100 to 200 cells were dissected from the extensor digitorum longus (EDL) muscle of control and CHF rats. Muscles from CHF rats exhibited depressed tension development compared with control muscles during twitches. Treatment with 2mM dibutyryl cyclic AMP returned tension and Ca2+ towards normal levels. There was no evidence of cellular atrophy in the CHF rats. In conclusion, EDL skeletal muscle from rats with CHF had intrinsic abnormalities in excitation-contraction coupling that could be reversed with cyclic AMP supplementation as previously reported for the heart. This suggests that deficient cyclic AMP levels may contribute to both cardiac and skeletal muscle dysfunction in CHF.

Animals↗
PubMed1996

Cervical dysplasia treatment: key issues for developing countries.

Many developing countries face serious obstacles that have hindered establishment of successful cervical cancer control programs. Various countries are now seeking to strengthen cytology services and identify simple low-cost screening strategies; but any real gains in reducing cervical cancer incidence and mortality will also require effective treatment of women with preinvasive disease. Despite a trend toward conservative outpatient approaches for treating cervical dysplasia in industrialized countries, clinicians in many developing countries still rely primarily on invasive inpatient methods such as cone biopsy and hysterectomy. For women who could be treated with less invasive methods, these procedures tend to pose unnecessary risks and entail high costs that put them beyond the reach of many patients. Outpatient therapy, employing methods such as cryotherapy and the loop electrosurgical excision procedure (LEEP), combined with proper follow-up, is appropriate for dealing with visible lesions on the ectocervix when invasive cancer and endocervical involvement have been ruled out. Cryotherapy and LEEP hold out particular promise for developing countries because of their effectiveness, lack of side-effects, simplicity, and low cost. Cure rates range from 80% to 95%, depending on the method used and the severity of the lesions. However, each method has advantages and disadvantages that demand consideration. Various ways of reducing the number of follow-up visits, including the two-visit "see and treat" approach, are also available for use in areas where women's access to health services may be limited. A recent survey by the Program for Appropriate Technology in Health (PATH) affirmed the tendency to rely on cone biopsy and hysterectomy. It also found that in many places all degrees of preinvasive disease were treated, rather than only high-grade or severe conditions; that respondents in Latin America, the Caribbean, and Asia tended to use cryotherapy and LEEP more widely than other low-cost methods; that LEEP was preferred over cryotherapy in Latin America; and that colposcopes and other basic equipment needed to provide treatment were not consistently or widely available in some settings.

Colposcopy↗
PubMed1995

Inhibition of redox cycling of methoxatin (PQQ), and of superoxide release by phagocytic white cells.

The iodonium compounds diphenyleneiodonium and diphenyliodonium, and the amine compounds, 4,5-dimethyl phenylene diamine, N,N-dimethyl 1,4-phenylene diamine, 1,2-diamino-4,5-methyleneoxybenzene, and aminomalononitrile inhibit methoxatin's (PQQ's) redox activity in vitro, that is, the methoxatin-coupled oxidation of glycine and reduction of nitroblue tetrazolium to formazan. The compounds mentioned above also inhibit phorbol myristate acetate (PMA) stimulated superoxide release by phagocytic white cells--determined mainly as the superoxide dismutase sensitive reduction of ferricytochrome C. Related compounds, 3,4-diaminopyridine and 4-dimethylamino-benzylamine, did not inhibit redox activity of PQQ in vitro, nor did they inhibit PMA stimulated superoxide production in monocytes or neutrophils. Thus, there is a correlation between an agent's ability to inhibit PQQ redox cycling and its ability to inhibit superoxide release by phagocytes. The findings are a further indication that PQQ is involved in the respiratory burst of phagocytic cells.

Amines↗
PubMed1995

Stroke rate is markedly reduced after carotid endarterectomy by avoidance of protamine.

PURPOSE: Postoperative neurologic injury remains a significant risk of carotid endarterectomy. Mechanisms include embolization of debris and formation of thrombus on the newly endarterectomized surface. We hypothesized that the risk of postoperative neurologic injury would be lower in those patients who did not receive protamine for reversal of heparin anticoagulation. METHODS: We reviewed 348 consecutive primary carotid endarterectomies performed since January 1, 1986, to determine the relationship between surgical outcomes and reversal of heparin anticoagulation. Patients undergoing additional simultaneous cardiovascular procedures were excluded. One hundred ninety-three patients received protamine after completion of the endarterectomy. The remaining 155 patients did not receive any protamine. RESULTS: All patients in both groups survived to discharge. There were no strokes in those patients who did not receive any protamine; however, the stroke rate in the protamine group was 2.6% (5 of 193), p < 0.045. The incidence of hematoma requiring reexploration was 1.0% (2 of 193) and 1.9% (3 of 155) in the protamine and no-protamine groups, respectively (p = NS). Intraoperative shunting was used more frequently in the no-protamine group (84% vs 67%, p < 0.001), and patch angioplasty was performed more frequently in the protamine group (35% vs 15%, p < 0.001). However, neither shunting nor patching significantly influenced stroke rates. CONCLUSIONS: We conclude that carotid endarterectomy without reversal of heparin anticoagulation is associated with a reduced postoperative stroke rate without a significant increase in morbidity rates.

Aged↗
PubMed1995

Last occurrence and survival during winter of the arbovirus vector Culicoides brevitarsis at the southern limits of its distribution.

Linear regression analysis was used to describe the decline in numbers of Culicoides brevitarsis Kieffer into winter with monthly maximum, average and minimum temperatures at the southern limits to its distribution in New South Wales. From this, low temperature thresholds were derived when C brevitarsis would be absent from the field. The low minimum threshold +/- 2 SE (95% Confidence Interval) of 8.1 +/- 0.3 degree C was used with historical temperature data to estimate the last month that the species should occur (March to June) and the mean number of months (2 to 6.5) below the threshold at 17 selected sites. Probability for survival during winter at these sites was estimated from years when the number of consecutive months below the threshold was < or = 2 months. This varied from zero to 51% depending on the location of the site. Last occurrence was 0.7 months later on average and absolute probabilities for survival ranged from zero to 100% when the temperatures were increased by an arbitrary 2 degrees C.

Animals↗