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Biomedical subjects

Alan Murray

Publications and source records attributed to Alan Murray.

At least 37 records · Page 2Linked to original sources
PubMed2004

Effect of premature ventricular beats on manual and automatic repolarization measurements.

OBJECTIVE: To compare QT interval and QT dispersion in ventricular ectopic beats with measurements from the preceding and the immediately following sinus beats, and investigate differences between manual and automatic measurements. PATIENTS: Eleven chronic uremic patients. MAIN OUTCOME MEASURES: ECGs were recorded during hemodialysis treatment and 12-lead sections containing five consecutive beats were extracted, each containing four sinus beats and one centrally-positioned premature ventricular beat. QT measurements were performed both manually and with a computer-automated technique. RESULTS: T wave amplitude was greater in the ectopic beats compared to the sinus beats (0.61 +/- 0.18 vs. 0.23 +/- 0.06 mV, P <.001). The ectopic beats had a greater QT than the sinus beats when measured manually (415 +/- 35 ms vs. 386 +/- 28 ms, P <.001), or automatically (375 +/- 30 vs. 366 +/- 27 ms, P<.01). The sinus beats following the ectopics had a greater QT than the preceding sinus beats (400 +/- 27 vs. 386 +/- 28 ms, P<.001, manual; 382 +/- 24 vs. 366 +/- 27 ms, P<.001, automatic). Differences in QT dispersion were seen only between the ectopic and sinus beats (91 +/- 31 vs. 58 +/- 27 ms, P <.001, manual; 68 +/- 33 vs. 49 +/- 35 ms, P <.001, automatic). CONCLUSIONS: Manual measurement resulted in greater QT values than automatic measurement. Both techniques identified differences between sinus and ectopic beats. The ventricular ectopic beats resulted in an increase in the QT of the immediately following sinus beats. These results confirm the need to interpret QT measurements with care in the presence of ectopic beats.

Aged↗
PubMed2004

Magnetocardiography for pharmacology safety studies requiring high patient throughput and reliability.

Recent guideline drafts of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) underline the necessity to test nonantiarrhythmic drugs for their potential to prolong the QT or the corrected QT (QTc) interval. The implementation of these guidelines requires a large amount of ECG measurements on animals and humans in preclinical and clinical phases of the drug development process. We propose the use of magnetocardiography (MCG) as a complementary method with particular advantages in high-throughput studies, where signal quality and reliability are key factors. Our proposal is based on a review of recent MCG studies investigating the repolarization phase and results of methodological work assessing QT interval parameters from the MCG. The applicability of MCG for pre-clinical in-vivo studies is demonstrated by the ease of measurement in unrestrained non-anesthetized rabbits, guinea pigs, and hamsters..

Animals↗
PubMed2004

Surface atrial frequency analysis in patients with atrial fibrillation: a tool for evaluating the effects of intervention.

INTRODUCTION: The aims of this study were to evaluate (1) principal component analysis as a technique for extracting the atrial signal waveform from the standard 12-lead ECG and (2) its ability to distinguish changes in atrial fibrillation (AF) frequency parameters over time and in response to pharmacologic manipulation using drugs with different effects on atrial electrophysiology. METHODS AND RESULTS: Twenty patients with persistent AF were studied. Continuous 12-lead Holter ECGs were recorded for 60 minutes, first, in the drug-free state. Mean and variability of atrial waveform frequency were measured using an automated computer technique. This extracted the atrial signal by principal component analysis and identified the main frequency component using Fourier analysis. Patients were then allotted sequentially to receive 1 of 4 drugs intravenously (amiodarone, flecainide, sotalol, or metoprolol), and changes induced in mean and variability of atrial waveform frequency measured. Mean and variability of atrial waveform frequency did not differ within patients between the two 30-minute sections of the drug-free state. As hypothesized, significant changes in mean and variability of atrial waveform frequency were detected after manipulation with amiodarone (mean: 5.77 vs 4.86 Hz; variability: 0.55 vs 0.31 Hz), flecainide (mean: 5.33 vs 4.72 Hz; variability: 0.71 vs 0.31 Hz), and sotalol (mean: 5.94 vs 4.90 Hz; variability: 0.73 vs 0.40 Hz) but not with metoprolol (mean: 5.41 vs 5.17 Hz; variability: 0.81 vs 0.82 Hz). CONCLUSION: A technique for continuously analyzing atrial frequency characteristics of AF from the surface ECG has been developed and validated.

Aged↗
PubMed2004

Characterization of the Korotkoff sounds using joint time-frequency analysis.

The sounds associated with the five classical Korotkoff phases are clinically important for measuring systolic and diastolic blood pressures. The frequency ranges of the sounds have already been described simply using the overall peak frequencies within each phase by Fourier methods. However, such analysis may be missing potentially useful clinical information. The aim of this study was to compare features associated with the different phases of the Korotkoff sounds obtained during blood pressure measurement using a joint time-frequency analysis (JTFA) technique. A single operator recorded Korotkoff sounds from 25 healthy subjects using a measurement system comprising cardiology stethoscope, microphone, amplifier and recording system for computer sound digitization, and a MiniDisc system for playback to the cardiologist for Korotkoff phase classification. We have shown that using this system the phase classification by the cardiologist is repeatable, with no significant differences found in the number of sounds allocated to phases on two separate recording assessments. The digitized sounds were processed using a MATLAB-based short-time Fourier transform JTFA technique and differences in time, frequency and amplitude characteristics between the phases compared. It was found that on average, phase III had the largest overall amplitude and high frequency energy. Phase II had the greatest high frequency component and longest murmur, and was visibly the most complex phase in terms of time and frequency content. In contrast, phases IV and V had the lowest amplitude and frequency components. Overall, the statistically significant transitions between phases were: phase I to II with increases in high frequency (224 to 275 Hz) (p < 0.01) and sound duration (49 to 98 ms) (p < 0.0001), II to III with a significant decrease in sound duration (to 37 ms) (p < 0.0001), III to IV with decreases in maximum amplitude (0.95 to 0.25), highest frequency (262 to 95 Hz), and relative high frequency energy of the sounds (0.61 to 0.10) (all p < 0.0001), and IV to V with decreases in the maximum amplitude (0.25 to 0.13) (p < 0.0002) and high frequency energy (0.10 to 0.03) (p < 0.005). This study has demonstrated that joint time-frequency analysis of Korotkoff sounds was able to identify characteristic differences associated with the different phases classified by the expert cardiologist. Ultimately, exploiting the joint time and frequency characteristics of the sounds may improve blood pressure measurement and help to assess the stiffness of the peripheral arteries.

Arteries↗
PubMed2004

Effects on baroreflex sensitivity measurements when different protocols are used to induce regular changes in beat-to-beat intervals and systolic pressure.

Baroreflex sensitivity is becoming an important clinical measurement. Nevertheless there is no recommend standard measurement protocol. This study assessed the ability of eight protocols to induce regular changes in cardiac beat-to-beat interval and systolic pressure (SP), and the effect each protocol had on baroreflex sensitivity (BRS). Twelve subjects had changes in cardiac beat-to-beat intervals and SP levels induced at 8 times a minute by following 8 different protocols, each for 3 min. These comprised breathing in a supine and standing posture, breathing through a resistance, breathing into a closed orifice (the breathing protocols), and performing handgrip exercises, being rocked, having legs raised and lowered, and being presented with mental arithmetic questions (the non-breathing protocols). Induction success of each protocol was determined by the percentage of cardiac beat-to-beat interval and SP level signals with a peak at 8 times per minute in their frequency spectra. The consistency of the induced changes was measured by a signal-to-noise ratio (SNR). BRS was calculated from the frequency spectra. The induction success was 85% for breathing and 31% for non-breathing protocols. The consistency of cardiac beat-to-beat interval changes was highest with supine breathing (SNR = 1.6 +/- 0.3) and resistance breathing (SNR = 1.5 +/- 0.5) protocols. The consistency of SP level changes was highest with resistance breathing (SNR = 1.0 +/- 0.3) and breathing into a closed orifice (SNR = 1.0 +/- 0.5) protocols. BRS values in the supine breathing protocol (24 +/- 10 ms mmHg(-1)) and the handgrip protocol (32 +/- 3 ms mmHg(-1)) were significantly greater (p < 0.05) than for standing breathing (11 +/- 5 ms mmHg(-1)), resistance breathing (17 +/- 8 ms mmHg(-1)) or breathing into a closed orifice (12 +/- 5 ms mmHg(-1)) protocols. Different protocols have different induction successes and degrees of effectiveness in inducing cardiac beat-to-beat and SP level changes. BRS is affected by the induction protocol used, highlighting the need for a standard measurement protocol.

Adult↗
PubMed2004

Assessment of a technique to determine the mechanical properties of coronary arteries using mock arteries.

Heart disease is the leading cause of death in the western world, and percutaneous transluminal coronary angioplasty (PTCA) and stent deployment are standard procedures used to reopen and/or stabilize blocked coronary arteries. Despite considerable improvements in these techniques, restenosis is still a long term problem, with patients requiring repeated procedures. Hence, further investigation of the mechanisms that contribute to arterial wall remodelling may help to improve the success of percutaneous coronary interventions (PCI). The aim of this study was to assess a measurement technique for its ability to determine the compliance of mock arteries using different balloon catheters during a standard angioplasty procedure. Pressure-volume (PV) curves were used to determine the combined mechanical response of the system, the balloon catheters and mock arteries in real time. The validity of subtracting the system compliance from the PV curves containing the system, balloon and/or mock artery was assessed using two-independent measurement techniques to determine the balloon inflation volume. Eighteen balloon catheters from four different manufactures were inflated inside three mock arteries with differing compliances (high, medium, low) and the resulting PV curves were recorded. The compliances of the three mock arteries were then determined from the PV curves. The results were compared to reference values of the three mock arteries, which were determined from one of the independent mechanical tests. Corrections for each balloon catheter type and each individual balloon catheter were studied. A correlation coefficient of 0.99 between the two-independent volume measurement techniques confirmed the validity of subtracting the system compliance. The compliance values for the high, medium and low compliant mock arteries, obtained by using the different balloon catheters, varied between 4 and 12, 3 and 9 and, 2 and 5 (microl/bar) mm(-1), respectively. Standard deviation varied from 0.1 up to 2.1 (microl/bar) mm(-1). This was equivalent to a mean variation factor (root mean square/mean) of 29%, which reduced to 12% with correction. The system was always able to detect differences between mock arteries in spite of the large variation with different balloon catheters. The study has shown that it is possible to determine compliances of different mock arteries using different balloon catheters. However, the determined compliances needed to be corrected for different mechanical properties of the balloons used.

Angioplasty, Balloon, Coronary↗
PubMed2003

Comparison of automatic repolarization measurement techniques in the normal magnetocardiogram.

Multichannel MCG noninvasively measures cardiac magnetic field strength from many sites at the body surface, potentially providing useful regional information about ventricular repolarization. Previous work on ECGs has shown that automatic techniques for repolarization measurement are better than manual measurement at discriminating patients with cardiac conditions from normal subjects. Although automatic repolarization measurement techniques have been quantified for ECGs, no comparative data exists for the MCG. In this study four different automatic repolarization (QT) interval techniques for detecting T wave end in the MCG were compared. The influence of MCG filtering on the automatic algorithms was also quantified. MCGs were obtained at 49 sites over the heart from 23 normal subjects. Automatic measurements of the repolarization (QT) interval were made following the addition of different high pass (0.25, 0.5, 1 Hz) and low pass (100, 60, 40, 30 Hz) filters. There were consistent differences between automatic techniques in the unfiltered data amounting to greatest mean difference of 52.3 ms. Low pass filtering significantly increased the automatic repolarization (QT) interval relative to unfiltered measurement by 6.5 (3.2) ms (mean SD) for 100 Hz, 6.0 (3.0) ms for 60 Hz, 8.1 (3.2) ms for 40 Hz, and 8.8 (3.1) ms for 30 Hz across all techniques. High pass filtering significantly decreased the value by -2.6 (6.0) ms for 0.25 Hz, -5.5 (5.3) ms for 0.5 Hz, and -17.1 (7.8) ms for 1 Hz. Automatic measurements of repolarization (QT) in the MCG differ between techniques and are influenced by filtering. These effects should be considered when comparing results.

Analysis of Variance↗
PubMed2003

Age-related changes in the characteristics of the photoplethysmographic pulse shape at various body sites.

It is accepted that older subjects have increasing arterial stiffness resulting in changes in the propagation of the pulse to the periphery, and thereby influencing the peripheral pulse timing and shape characteristics. However, this age association with pulse shape is less clear in younger subjects and for different peripheral measurement sites. The aim of this study was to determine the association between age and changes in pulse shape characteristics at the ears, fingers and toes. Photoplethysmography pulse waveforms were recorded non-invasively from the right and left sides at the ears, index fingers and great toes of 116 normal healthy human subjects. Their median age was 41 years (range 13-72) allowing four distinct age groups to be considered (subjects younger than 30 years, 30-39 years, 40-49 years and 50 years of age or older). Normalized ear, finger and toe pulse shapes were calculated, for the whole subject group, and for the subjects within each age group. The differences in shape, relative to the oldest group, were also calculated for two distinct regions of interest: the systolic rising edge and the dicrotic notch of the pulse. Subtle, gradual and significant changes in the pulse shape were found at all sites with overall elongation of the systolic rising edge (p < 0.05) and damping of the dicrotic notch (p < 0.05) with age. The overall age-related changes in multi-site PPG pulse shape characteristics at the ear, finger and toe sites have been demonstrated and quantified. Age-matched normal ranges must be considered when evaluating pulses from patients with possible vascular disease.

Adolescent↗
PubMed2003

Tuberculosis in seals caused by a novel member of the Mycobacterium tuberculosis complex: Mycobacterium pinnipedii sp. nov.

A comparison of Mycobacterium tuberculosis complex isolates from seals (pinnipeds) in Australia, Argentina, Uruguay, Great Britain and New Zealand was undertaken to determine their relationships to each other and their taxonomic position within the complex. Isolates from 30 cases of tuberculosis in six species of pinniped and seven related isolates were compared to representative and standard strains of the M. tuberculosis complex. The seal isolates could be distinguished from other members of the M. tuberculosis complex, including the recently defined 'Mycobacterium canettii' and 'Mycobacterium caprae', on the basis of host preference and phenotypic and genetic tests. Pinnipeds appear to be the natural host for this 'seal bacillus', although the organism is also pathogenic in guinea pigs, rabbits, humans, Brazilian tapir (Tapirus terrestris) and, possibly, cattle. Infection caused by the seal bacillus is predominantly associated with granulomatous lesions in the peripheral lymph nodes, lungs, pleura, spleen and peritoneum. Cases of disseminated disease have been found. As with other members of the M. tuberculosis complex, aerosols are the most likely route of transmission. The name Mycobacterium pinnipedii sp. nov. is proposed for this novel member of the M. tuberculosis complex (the type strain is 6482(T)=ATCC BAA-688(T)=NCTC 13288(T)).

Animals↗
PubMed2002

Origin on the electrocardiogram of U-waves and abnormal U-wave inversion.

AIMS: Soon after the initial development of electrocardiography, U-waves were discovered in many normal subjects following the T-wave repolarisation waveform on the electrocardiogram. Various explanations have been offered for their origin, but none is universally accepted. We used our model of left ventricular repolarisation to explore the most common hypotheses for the genesis of U-waves. METHODS: Recently, we have shown that a computer model of left ventricular repolarisation was able to explain the formation of the characteristic shape of the T-wave, and we have now used this model to explore the most common hypotheses for the genesis of U-waves. The repolarisation phase of the action potentials in the model exhibited an after-potential. We investigated separately the effect on the 12-lead electrocardiogram of three different features of the model: the amplitude of the after-potential; dispersion of repolarisation in the left ventricle ranging from 20 to 100 ms; the timing of the after-potential, relative to the end of the principal action potential component, ranging from -100 to 100 ms. RESULTS: We show that delaying repolarisation in different regions of the heart cannot explain the U-wave, but show that the presence of after-potentials on the cardiac action potential do explain the U-wave polarity and other characteristic U-wave features. We also show that abnormal after-potential timing corresponds with abnormal U-wave inversion. CONCLUSION: Our model provides a realistic and simple solution to the problem of U-wave genesis.

Action Potentials↗
PubMed2002

The forgotten Korotkoff phases: how often are phases II and III Present, and how do they relate to the other Korotkoff phases?

BACKGROUND: There are no data on the pattern of the Korotkoff phases in the normal population. This study was designed to describe the pattern of Korotkoff phase distribution in adults and children; to measure the duration of each of the phases; and to describe the differences between adults and children. METHODS: A total of 57 children (7 to 8 years old) and 59 adults (median age 47 years, range 30 to 62 years) were studied. The pressure in the arm cuff was deflated using a device to provide a consistent deflation rate. The Korotkoff sounds were recorded to MiniDisc from the bell of a stethoscope and each sound described as phase I, II, III, or IV. RESULTS: The most common pattern of Korotkoff phase distribution was for all five phases to be present (children [23/57; 40%], adults [24/59; 41%]). Phases I and IV were more common in children than in adults (56/57 [98%] v 47/59 [80%]; P = .002 for phase I; 52/57 [91%] v 44/59 [75%]; P = .018 for phase IV). Phases II and III were less common in children than in adults (32/57 [56%] v 50/59 [85%], P = .001 for phase II; 27/57 [47%] v 45/59 [76%], P = .001 for phase III). Phases I and IV were longer in children (median 3.9 [interquartile range, IQR 2.1 to 6.7] and 6.7 [IQR 3.2 to 9.8] sec, respectively) compared with adults (1.3 [IQR 0.7 to 2.7] and 1.7 [IQR 0.3 to 2.6), P < .001). CONCLUSIONS: There are clear differences in the Korotkoff phases between adults and children. The length of phases II and III increase with age with concomitant decrease in phases I and IV. These differences between adults and children remain unexplained.

Adult↗
PubMed2002

Errors in repolarization measurement using magnetocardiography.

Multichannel magnetocardiography (MCG) noninvasively measures variations in magnetic field strength from many sites at the body surface, potentially providing useful regional information about ventricular repolarization. MCGs contain features similar to ECGs, and although errors associated with repolarization measurement have been quantified for ECGs, no comparative data exists for MCGs. In this study, errors in manual measurement of repolarization interval in the MCG were determined. Sixteen MCG channels and three ECG leads were recorded simultaneously in eight healthy subjects. Each recording was displayed in a random order on a computer screen, in presentations with different noise levels, time display widths, and amplitude display heights. In total, manual measurement of repolarization intervals in 2,048 (eight subjects x 16 channels x eight presentations x two repeats) MCGs were made by each of four analysts. Measured repolarization intervals were reduced by 3 ms when noise was added and by a further 3 ms when this noise was doubled. Intervals were shortened by 9 ms when the time display width was doubled and by a further 10 ms when the display width was doubled again. Measurements increased by 7 ms for a doubling of amplitude display height, equivalent to a doubling of T wave height. There were also consistent differences between analysts; amounting to a greatest mean difference of 24 ms. Display characteristics, added noise, and different analysts thus affect manual repolarization interval measurements in MCG. The errors detected demonstrate the importance of a standard presentation for repolarization measurement in the MCG.

Electrocardiography↗
PubMed2002

Quantification of T wave shape changes following exercise.

T wave shape is increasingly used to provide insights into cardiac repolarization and, although shape is known to change as heart rate changes, there are no published quantitative clinical data. The aim of this study was to quantify these changes. Heart rate (HR), T wave amplitude, and two measures of T wave symmetry (SRarea--ratio of areas about the peak, SRtime--ratio of centrality of peak), were quantified over a period of 360 seconds following exercise in 20 healthy human subjects. As HR decreased, in all subjects the T wave became more asymmetrical (SRarea 20/20, SRtime 20/20, P < 0.0001). Resting reference HR and symmetry ratios were (mean +/- SD), HR 63 +/- 10 beat/min, SRarea 1.68 +/- 0.25, and SRtime 2.13 +/- 0.39. Fifty seconds postexercise, HR was significantly higher than reference at 92 +/- 11 beat/min (P < 0.0001), and symmetry ratios were significantly less at SRarea 1.04 +/- 0.15, SRtime 1.24 +/- 0.36 (P < 0.0001). Significant differences in HR and both symmetry ratios remained at 300 seconds postexercise. Amplitude increases had returned to their reference values at 300 seconds. T wave shape was significantly more symmetrical at higher HRs. These findings confirm qualitative reports of shape changes.

Adult↗
PubMed2002

Effect of changes in heart rate and in action potential duration on the electrocardiogram T wave shape.

The mechanisms responsible for changes in T wave symmetry and amplitude with changes in heart rate and action potential duration were investigated. A computer model of normal left ventricular repolarization was used to simulate the T waves on the surface 12-lead ECG. The effect of heart rate changes was studied by varying the ratio between dispersion of repolarization (Disp) and action potential repolarization duration (APRD). With constant dispersion. as heart rate increases, APRD decreases and the ratio Disp/APRD increases. T waves were simulated while varying the Disp/APRD ratio from 3.6% to 100%. The T wave symmetry ratio measured from the areas either side of the peak (SRarea), the symmetry ratio from the times either side of the peak (SRtime) and the T wave amplitude (Tamplitude) were calculated from each simulated ECG. SRarea decreased from 1.42 to 0.77, SRtime from 1.75 to 1.04 and the Tamplitude increased from 0. 19 mV to 2.30 mV. The stability of results with variation in model characteristics was also investigated, by moving the heart +/- 20 mm on all three axes, rotating the heart axes by +/- 10 and by modifying all constants defining the action potential by +/- 5% and +/- 10%. T wave amplitude was sensitive to changes in heart position, as the heart was moved towards the body surface. However, T wave shape changed very little with heart position or rotation, with the SD of SRarea varying by less than 0.05 over an SRarea range of 0.65 for different values of Disp/APRD ratio. We have shown from our model that cardiac T waves increase in amplitude, and become more symmetric with their peaks becoming central as APRD shortens with increasing heart rate, agreeing with clinical observations. These results help to explain the T wave shape changes which occur when heart rate increases.

Action Potentials↗
PubMed2002

Microvascular blood flow and skin temperature changes in the fingers following a deep nspiratory gasp.

The aims of this study were to quantify the changes in finger pulp skin temperature, laser Doppler flow (LDF, microvascular flux) and photoplethysmogram (PPG, microvascular blood volume pulsatility), induced by a deep inspiration in healthy subjects, and to investigate the repeatability of these responses within a measurement session and between measurement sessions on separate days. A system comprising an electronic thermometer, a laser Doppler flowmeter and a PPG amplifier measured simultaneous vasoconstrictor responses to a deep inspiratory gasp from three adjacent fingers of one hand. Clearly defined responses were obtained in 15 of the 17 subjects studied. Skin temperature fell in all of these subjects after each gasp, with a median fall of 0.089 degrees C (P < 0.001). The median value of LDF flux reduction was 93% (P < 0.001) indicating a momentary almost complete shut-down of microvascular blood flow; and PPG also showed a large response relative to pulse amplitude of 2.6 (P < 0.001). The median times for waveforms to reach their minimum were 4.6 s (PPG), 6.3 s (LDF) and 29.1 s (skin pulp temperature), with median delays between minima of LDF and PPG of 1.6 s (P < 0.001) and skin temperature and PPG of 23.5 s (P < 0.001). The vascular responses of skin temperature, LDF and PPG to an inspiratory gasp were repeatable, with temperature change repeatable to within 10% of the median subject change.

Adult↗
PubMed2002

Fractal analysis in the detection of colonic cancer images.

The aim of this study was to investigate the value of fractal dimension in separating normal and cancerous images, and to examine the relationship between fractal dimension and traditional texture analysis features. Forty-four normal images and 58 cancer images from sections of the colon were analyzed. A "leave-one-out" analysis approach was used to classify the samples into each group. With fractal analysis there was a highly significant difference between groups (p < 0.0001). Correlation and entropy features showed greater differences between the groups (p < 0.0001). Nevertheless, the addition of fractal analysis to the feature analysis improved the sensitivity from 90% to 95% and specificity from 86% to 93%.

Case-Control Studies↗
PubMed2000

Identification of an immunogenic 18-kDa protein of Helicobacter pylori by alkaline phosphatase gene fusions.

The use of alkaline phosphatase fusion methodology to identify Helicobacter pylori exported proteins enabled the identification of an open reading frame (ORF) encoding a highly immunogenic, previously uncharacterised exported protein. The predicted aminoacid sequence displays a typical N-terminal signal peptide and contains regions of C-terminal hydrophobicity consistent with a membrane-associated protein. Southern blot analysis revealed that the gene encoding the protein was absent in several Helicobacter spp. and a combination of PCR and sequence analysis of the amplified gene showed that it is highly conserved amongst isolates of H. pylori. To obtain pure recombinant protein, the gene encoding the protein was cloned and expressed as a beta-galactosidase (beta-gal) fusion in Escherichia coli and the protein was purified by affinity chromatography and proteolytic cleavage of the beta-gal portion. The purified protein, which has an apparent mol. wt of 18 kDa, was recognised by antibody present in 71% of sera from patients infected with H. pylori, but in only 16% of sera from patients with unrelated or no gastrointestinal disease, by Western blot assays. These results indicate that the 18-kDa protein from H. pylori is immunogenic and is expressed in vivo.

Alkaline Phosphatase↗