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Biomedical subjects

G D Bell

Publications and source records attributed to G D Bell.

At least 19 recordsLinked to original sources
PubMed1992

The inhibition of the oxidation of low density lipoprotein by (+)-catechin, a naturally occurring flavonoid.

(+)-Catechin inhibited the copper-catalysed oxidation of human low density lipoprotein (LDL) in a dose-dependent manner with complete inhibition at 20 micrograms/mL. The flavonoid at a concentration of 50 micrograms/mL also inhibited oxidation of LDL induced by the mouse transformed macrophage J774, human monocyte-derived macrophages and vascular endothelial cells isolated from human umbilical cords. LDL modified by copper-catalysed or cell-induced oxidation was endocytosed and degraded by human macrophages at a much greater rate than native LDL. LDL reisolated from copper or cell incubations in the presence of (+)-catechin was endocytosed and degraded at rates similar to native LDL. (+)-Catechin appeared to inhibit the uptake and degradation by macrophages of cell-modified LDL. The actions of (+)-catechin on cell-induced oxidation of LDL are consistent with the ability of flavonoids of similar structure to inhibit lipoxygenases and with a role for lipoxygenases in cell-induced modification of LDL in vivo.

Animals↗
PubMed1992

A comparative study of simultaneous vibromyography and electromyography with active human quadriceps.

Vibromyographic (VMG) signals, which are low-frequency vibration signals generated during muscle contraction, were studied in comparison with electromyographic (EMG) signals recorded simultaneously during isometric contraction of the human quadriceps muscles. The comparison was accomplished by evaluating the averaged root mean squared (rms) value, mean frequency (MF), and peak frequency (PF) of the VMG and EMG signals for four muscle contraction levels at joint angles of 30 degrees, 60 degrees, and 90 degrees. The four contraction levels, namely 20, 40, 60, and 80% of maximum voluntary contraction (MVC), were estimated and controlled by the torque readings of a Cybex II dynamometer. It was found that the VMG and EMG under the same conditions on the same muscle group are in general equally sensitive to the levels of muscle contraction. Results show that the rms value of the VMG signal increases linearly, in a manner similar to the EMG rms/%MVC relationship, with increasing muscle contraction levels. Furthermore, the study indicates that the averaged MF (6-24 Hz) and PF (9-19 Hz) of the VMG signals are much lower than the MF (75-109 Hz) and PF (40-80 Hz) of the EMG signals. The slopes of MF/%MVC curves for the VMG and EMG are approximately the same for 60 degrees and 90 degrees joint angles (approximately 3.1 Hz per 20% MVC for VMG and approximately 2.6 Hz per 20% MVC for EMG).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Analysis of knee vibration signals using linear prediction.

Clinical methods used at present for the diagnosis of cartilage pathology in the knee are invasive in nature, and carry some risks. There exists a need for the development of a safe, objective, noninvasive method for early detection, localization, and quantification of cartilage pathology in the knee. This paper investigates the possibility of developing such a method based on an analysis of vibrations produced by joint surfaces rubbing against one another during normal movement. In particular, the method of modeling by linear prediction is used for adaptive segmentation and parameterization of knee vibration signals. Dominant poles are extracted from the model system function for each segment based on their energy contributions and bandwidths. These dominant poles represent the dominant features of the signal segments in the spectral domain. Two-dimensional feature vectors are then constructed using the first dominant pole and the ratio of power in the 40-120 Hz band to the total power of the segment. The potential use of this method to distinguish between vibrations produced by normal volunteers and patients known to have cartilage pathology (chondromalacia) is discussed.

Auscultation↗
PubMed1992

Mathematical modeling and spectrum analysis of the physiological patello-femoral pulse train produced by slow knee movement.

Analysis of vibration signals emitted by the knee joint has the potential for the development of a noninvasive procedure for the diagnosis and monitoring of knee pathology. In order to obtain as much information as possible from the power density spectrum of the knee vibration signal, it is necessary to identify the physiological factors (or physiologically relevant parameters) that shape the spectrum. This paper presents a mathematical model for knee vibration signals, in particular the physiological patello-femoral pulse (PFP) train produced by slow knee movement. It demonstrates through the mathematical model that the repetition rate of the physiological PFP train introduces repeated peaks in the power spectrum, and that it affects the spectrum mainly at low frequencies. The theoretical results also show that the spectral peaks at multiples of the PFP repetition rate become more evident when the variance of the interpulse interval (IPI) is small, and that these spectral peaks shift toward higher frequencies with increasing PFP repetition rates. To evaluate the mathematical model, a simulation algorithm was developed, which generates PFP signals with adjustable repetition rate and IPI variance. Signals generated by simulation were seen to possess representative spectral characteristics typically observed in physiological PFP signals. This simulation procedure allows an interactive examination of several factors which affect the PFP train spectrum. Finally, in vivo measurements of physiological PFP signals of normal volunteers are presented. Results of simulations and analysis of signals recorded from human subjects support the mathematical model's prediction that the IPI statistics play a very significant role in determining the low-end power spectrum of the physiological PFP signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1992

Does a previous course of tripotassium dicitrato bismuthate affect the subsequent chances of successful Helicobacter pylori eradication?

We have performed a retrospective study of 103 patients with either peptic ulcer or non-ulcer dyspepsia, infected with metronidazole-sensitive strains of Helicobacter pylori (H. pylori), who were treated with a combination of tripotassium dicitrato bismuthate and metronidazole for a period of at least two weeks. Dual therapy with tripotassium dicitrato bismuthate plus metronidazole showed similarly high eradication rates (greater than or equal to 80%) of H. pylori from patients irrespective of age, gender or clinical diagnosis. Most importantly, dual therapy achieved a similar eradication rate of H. pylori infection in 41 patients who had previously been treated with tripotassium dicitrato bismuthate alone or in combination with an antibiotic other than metronidazole. It therefore appears that H. pylori does not become resistant to treatment with tripotassium dicitrato bismuthate.

Adult↗
PubMed1992

Experience with 'triple' anti-Helicobacter pylori eradication therapy: side effects and the importance of testing the pre-treatment bacterial isolate for metronidazole resistance.

At the 1990 World Congresses of Gastroenterology, the Working Party on Helicobacter pylori (H. pylori) recommended that, in suitable patients, the bacterium should be eradicated using a therapeutic regimen comprising a bismuth salt, tetracycline and metronidazole for two weeks. We have treated 40 patients infected with H. pylori with 'triple' therapy consisting of 120 mg tripotassium dicitrato bismuthate q.d.s., 500 mg tetracycline q.d.s. and 400 mg metronidazole t.d.s. for two weeks. The success rate, in terms of bacterial eradication, was 19/21 (90.5%) in patients with metronidazole-sensitive organisms, compared with only 6/19 (31.6%) in patients whose H. pylori were resistant to metronidazole (P less than 0.01). Side effects, particularly diarrhoea and vomiting/nausea, were common: 23/40 patients reported such symptoms during the 14-day course of therapy. Fifteen of these 23 patients completed the entire 14-day course, although suffering from significant side effects, while the remaining eight patients had to discontinue the treatment because side effects became intolerable. If a form of triple therapy is going to be widely used to eradicate H. pylori infection, the regimen will have to be simpler, shorter, produce fewer side effects and be more effective in patients with metronidazole-resistant bacteria.

Adult↗
PubMed1992

Short report: omeprazole plus antibiotic combinations for the eradication of metronidazole-resistant Helicobacter pylori.

Twenty-eight Helicobacter pylori-positive patients with metronidazole-resistant isolates and 25 with metronidazole-sensitive isolates were treated for 14 days with 40 mg omeprazole nocte plus 500 mg amoxycillin t.d.s. Eradication of H. pylori, defined as absence of the organism one month after cessation of treatment, was assessed using the [14C]urea breath test. The eradication rate in patients with metronidazole-resistant isolates was 14/28 (50%) while that in patients was metronidazole-sensitive isolates was 12/25 (48%). In contrast to these encouraging eradication rates, very poor results were obtained with a 7-day course of omeprazole (40 mg nocte) in combination with erythromycin ethylsuccinate (500 mg q.d.s.) and tripotassium dicitrato bismuthate tablets (120 mg q.d.s.). The latter eradication rates were 3/20 (15%) in patients taking erythromycin tablets and 3/19 (16%) in those taking a liquid formulation of erythromycin. All treatment regimens were well tolerated and all patients completed the prescribed course of therapy.

Adult↗
PubMed1991

Monitoring and safety in endoscopy.

Over 50% of the complications and 60% of the deaths associated with upper GI endoscopy are cardiopulmonary in type. Oxygen desaturation and cardiac arrhythmias at the time of endoscopy are common. Ways of trying to prevent hypoxia occurring are discussed. The most effective of these is the use of supplemental oxygen. Pulse oximeters are being used increasingly frequently by endoscopists. The way in which oximeters work is described in some depth, as are some of the potential errors that may result from their use. The author believes that, as in anaesthetic practice, pulse oximeters will be used ever more frequently by endoscopists and finally become standard equipment in all endoscopy units. The case for using continuous ECG monitoring and blood pressure measurement is briefly discussed. The ASGE have recently published their recommendations on monitoring patients undergoing GI endoscopic procedures. The BSG's own working party on safety and monitoring is in the process of finalizing its recommendations, and the final part of the chapter discusses the views of this working party and gives some insight into what its final recommendations are likely to be.

Arrhythmias, Cardiac↗
PubMed1991

Omeprazole and Helicobacter pylori: temporary suppression rather than true eradication.

Twenty-four Helicobacter pylori (H. pylori)-positive patients were treated for 28 days with either 20 mg omeprazole o.m. (n = 12) or 40 mg omeprazole o.m. (n = 12). Clearance (absence of H. pylori at the end of or shortly after treatment) and eradication (absence of H. pylori 1 month after cessation of treatment) were assessed using the 14C-urea breath test. Observed clearance and eradication were: 20 mg omeprazole 3/12 and 0/12; 40 mg omeprazole 6/12 and 1/12 respectively. The effect on H. pylori is probably due to the change in gastric pH from acid to neutral, however it is insufficient to recommend the inclusion of omeprazole in regimens aimed at eradicating H. pylori.

Adult↗
PubMed1991

Pattern of breathing during upper gastrointestinal endoscopy: implications for administration of supplemental oxygen.

Cardiopulmonary complications account for half the deaths associated with upper gastrointestinal endoscopy. The incidence of hypoxia at the time of upper gastrointestinal endoscopy can be greatly reduced by the administration of supplemental oxygen via nasal cannulae. Using dual thermistors in the mouth and nostrils of patients undergoing upper gastrointestinal endoscopy, the present study demonstrates that most patients breathe predominantly via the oral, rather than the nasal, route following intubation of the oesophagus. The implication from the study is that, if supplemental oxygen is to be used in 'at risk' patients, it would be logical to employ an oral, rather than nasal, route of administration.

Endoscopy, Gastrointestinal↗
PubMed1991

Helicobacter pylori: treatment with combinations of pivampicillin and tripotassium dicitrato bismuthate.

Fifty Helicobacter pylori- (H. pylori) positive patients entered an open study and were assigned to one of four treatment regimens comprising: pivampicillin (500 mg b.d.) for 2 weeks +/- tripotassium dicitrato bismuthate (tablet or liquid form) for one month. The 14C-urea breath test was used to evaluate clearance (negative at the end of treatment) and eradication (negative at 1 month post-treatment) of H. pylori. Clearance rates were 20% (2/10) after pivampicillin alone, 86% (12/14) after tripotassium dicitrato bismuthate tablets (240 mg b.d.) plus pivampicillin, 67% (6/9) after tripotassium dicitrato bismuthate tablets (120 mg q.d.s.) plus pivampicillin, and 100% (13/13) after tripotassium dicitrato bismuthate liquid (120 mg in 5 ml q.d.s) plus pivampicillin. The eradication rates were 0% (0/10), 13% (2/15), 0% (0/11) and 54% (7/13), respectively. Combination of the results from the 2 tripotassium dicitrato bismuthate tablet/pivampicillin groups gave an eradication rate of 7.7% (2/26) which was significantly lower than the 53.9% (7/13) obtained with tripotassium dicitrato bismuthate liquid/pivampicillin (P less than 0.02). In conclusion, a liquid tripotassium dicitrato bismuthate pivampicillin combination may be of special use in the treatment of H. pylori-positive patients when triple therapy is contraindicated (e.g. patient sensitivity/allergy to metronidazole) or when the H. pylori isolate is resistant to metronidazole.

Adult↗
PubMed1991

Sedation for upper gastrointestinal endoscopy: results of a nationwide survey.

A postal questionnaire inquiring about routine sedation and premedication practice for upper gastrointestinal endoscopy was sent to 1048 doctors. Of 665 appropriate returns, 81% were from consultant physicians and surgeons. Most endoscopists (90%) reported using an intravenous benzodiazepine for at least three quarters of endoscopies and 54% of physicians and 69% of surgeons always did so. Midazolam was the intravenous sedative used by a third of all respondents and 13% also used an additional intravenous agent, usually pethidine. Over the previous two years a total of 119 respiratory arrests, 37 cardiac arrests, and 52 deaths were identified. Adverse outcomes were reported more frequently by consultant physicians, by those who 'titrated' the intravenous sedative, and by those who used an additional intravenous agent, but were reported equally frequently by endoscopists using midazolam and endoscopists using diazepam. There is an urgent need for a prospective study to identify the circumstances and risk factors associated with adverse outcomes related to endoscopy.

Benzodiazepines↗
PubMed1991

Recommendations for standards of sedation and patient monitoring during gastrointestinal endoscopy.

(1) Safety and monitoring should be part of a quality assurance programme for endoscopy units. (2) Resuscitation equipment and drugs must be available in the endoscopy and recovery areas. (3) Staff of all grades and disciplines should be familiar with resuscitation methods and undergo periodic retraining. (4) Equipment and drugs necessary for the maintenance of airway, breathing, and circulation should be present in the endoscopy unit and recovery area (if outside the unit) and checked regularly. (5) A qualified nurse, trained in endoscopic techniques and adequately trained in resuscitation techniques, should monitor the patient's condition during procedures. (6) Before endoscopy, adverse risk factors should be identified. This may be aided by the use of a check list. (7) The dosage of all drugs should be kept to the minimum necessary. There is evidence that benzodiazepine/opioid mixtures are hazardous. (8) Specific antagonists for benzodiazepines and opioids exist and should be available in the event of emergency. (9) A cannula should be placed in a vein during endoscopy on 'at risk' patients. (10) Oxygen enriched air should be given to 'at risk' patients undergoing endoscopic procedures. (11) The endoscopist should ensure the well being and clinical observation of the patient undergoing endoscopy in conjunction with another individual. This individual should be a qualified nurse trained in endoscopic techniques or another medically qualified practitioner. (12) Monitoring techniques such as pulse oximetry are recommended. (13) Clinical monitoring of the patient must be continued into the recovery area. (14) Records of management and outcome should be collected and will provide data for appropriate audit.

Anesthesia Recovery Period↗