One-dimensional models of the human biliary system

This paper studies two one-dimensional models to estimate the pressure drop in the normal human biliary system for Reynolds number up to 20. Excessive pressure drop during bile emptying and refilling may result in incomplete bile emptying, leading to stasis and subsequent formation of gallbladder stones. The models were developed following the group's previous work on the cystic duct using numerical simulations. Using these models, the effects of the biliary system geometry, elastic property of the cystic duct, and bile viscosity on the pressure drop can be studied more efficiently than with full numerical approaches. It was found that the maximum pressure drop occurs during bile emptying immediately after a meal, and is greatly influenced by the viscosity of the bile and the geometric configuration of the cystic duct, i.e., patients with more viscous bile or with a cystic duct containing more baffles or a longer length, have the greatest pressure drop. It is found that the most significant parameter is the diameter of the cystic duct; a 1% decrease in the diameter increases the pressure drop by up to 4.3%. The effects of the baffle height ratio and number of baffles on the pressure drop are reflected in the fact that these effectively change the equivalent diameter and length of the cystic duct. The effect of the Young's modulus on the pressure drop is important only if it is lower than 400 Pa; above this value, a rigid-walled model gives a good estimate of the pressure drop in the system for the parameters studied.

Small Bowel Bacterial Overgrowth in Symptomatic Older People: Can It Be Diagnosed Earlier?

BACKGROUND/OBJECTIVES

In older people, small bowel bacterial overgrowth syndrome may be a common, but under-diagnosed, cause of diarrhoea and nutrient malabsorption. We aim to determine which clinical features and baseline laboratory investigations indicate a high likelihood of small bowel bacterial overgrowth as defined by a positive glucose breath test.

METHODS

A retrospective analysis of records for all patients referred for glucose breath test over a 6-year period to a teaching hospital.

RESULTS

Out of 197 referrals, 168 patient records were located and analysed (62 male, 106 female; median age 65). Patient characteristics predictive of a positive glucose breath test were: increasing age (p < 0.01), low serum vitamin B12 (p = 0.02), low serum albumin (p = 0.03), previous partial gastrectomy (p < 0.01), previous right hemi-colectomy (p < 0.01), presence of small bowel diverticulae (p = 0.01) and concurrent use of a proton pump inhibitor (p < 0.01). 52.5% (n = 21/40) of patients studied who were over 75 years old versus 21.8% (n = 28/128) of those under 75 years old had a positive glucose breath test (p < 0.01). The median time to diagnosis, from first hospital visit to positive glucose breath test, was 39 weeks.

CONCLUSIONS

There is often a significant delay in diagnosis of small bowel bacterial overgrowth. We suggest that this diagnosis should be considered earlier in the investigative algorithm in older patients with indicative symptoms and a predisposing factor (including previous partial gastrectomy, previous right hemi-colectomy, small bowel diverticulae or use of a proton pump inhibitor) or concurring laboratory indices (low vitamin B12 or albumin).

16-Detector multislice CT–skeletal scintigraphy image co-registration

OBJECTIVE

Co-registration of bone scintigrams with radiographs has been used in the diagnosis of wrist injuries, although co-registration of tomographic bone scintigraphy with computed tomography (CT) has not been widely reported. We describe a co-registration technique in patients with possible wrist fracture.

METHODS

The technique was used on three patients and involved placing the wrist on a Perspex board and tracing the outline of the forearm and hand with a pen to try and ensure accurate repositioning on the board for the two sets of imaging. Four point source markers were attached to the board during both examinations. Single photon emission computed tomography (SPECT) was performed 4 h after injection Tc-methylenediphosphonate (MDP), using a dual-headed gamma camera. CT images were acquired on a 16-detector CT unit. The SPECT and CT images were co-registered with commercially available image fusion software. The centre of the four markers was identified in both sets of images and a rigid body point match algorithm was used. Before patient studies, the technique was tested using a phantom.

RESULTS

In all the phantom and clinical studies it was possible to identify the positions of all the markers. There were varying degrees of success in patient repositioning.

CONCLUSION

We describe a technique that may aid the fusion of functional images from skeletal scintigraphy with the exquisite anatomical detail from the latest CT technology, in the detection of occult wrist fractures. The technique may aid fracture localization and/or detection and might help distinguish the clinically important scaphoid fractures from other benign carpal lesions.

The clinical pharmacokinetics of a new pharmacokinetically enhanced formulation of amoxicillin/clavulanate

BACKGROUND

A new oral pharmacokinetically enhanced formulation of the broad-spectrum antibiotic amoxicillin/clavulanate has been developed to provide more effective therapy against resistant pathogens than is provided by currently available formulations by maintaining therapeutically useful plasma amoxicillin concentrations for a longer period after dosing.

OBJECTIVE

This study explored the pharmacokinetics of the new oral formulation of amoxicillin/clavulanate in healthy male and female subjects.

METHODS

A single oral dose of pharmacokinetically enhanced amoxicillin/clavulanate (2000/125 mg; 16:1 ratio) was administered to subjects at the start of a meal. After dosing, blood samples were collected at frequent intervals up to 12 hours, and plasma was assayed for amoxicillin and clavulanate concentrations using validated procedures. The new formulation consisted of 1 layer of immediate-release amoxicillin and clavulanate and another of sustained-release amoxicillin in a proportion such that for an amoxicillin minimum inhibitory concentration (MIC) of 4 microg/mL, the time above the MIC (T >MIC) would be approximately > or = 40% over a 12-hour dosing interval.

RESULTS

The study enrolled 24 and 31 healthy male and female subjects, respectively. Their mean age was 35 years (range, 18-58 years) and mean body weight was 69 kg (range, 51-86 kg). After the expected sharp peak in plasma amoxicillin concentration, there appeared to be a slower decline with the pharmacokinetically enhanced formulation than is usually seen with conventional formulations, and there was evidence of a second amoxicillin absorption phase. The mean T >MIC for an amoxicillin MIC of 4 microg/mL was 49.4% of a 12-hour dosing interval, a value that cannot be achieved with existing approved doses and formulations of amoxicillin/clavulanate. By 12 hours, plasma amoxicillin concentrations were very low (approximately 0.05 microg/mL), suggesting no expectation of notable dose-to-dose accumulation on repeat dosing with a BID regimen. The terminal half-lives of amoxicillin (1.27 hours) and clavulanate (1.03 hours) with the new formulation were similar to those of existing formulations of amoxicillin/clavulanate. No deaths or serious adverse events were reported.

CONCLUSIONS

The enhanced pharmacokinetic profile of amoxicillin/clavulanate seen in this study suggests that this formulation is likely to be highly effective for the oral treatment of infections caused by bacteria--including beta-lactamase-producing organisms--and strains with amoxicillin MICs < or = 4 microg/mL.

Lack of effect of gemifloxacin on the steady-state pharmacokinetics of theophylline in healthy volunteers

Gemifloxacin is a novel fluoroquinolone, currently in development for the treatment of respiratory tract infections. This double-blind (with respect to gemifloxacin), randomized, crossover study investigated the possibility of pharmacokinetic interaction between gemifloxacin and theophylline. After a 4-8-day run-in phase to establish the dose of theophylline required to achieve a trough plasma concentration range of 8-15 mg/l, 15 healthy volunteers entered a randomized treatment phase. Volunteers then received oral theophylline, 300-400 mg twice daily, for 22 days. On days 5-11 and 16-22, they also received either placebo or gemifloxacin, 320 mg p.o. once daily, in a crossover fashion. Blood samples were collected up to 12 h after the morning dose of theophylline on days 11 and 22. Theophylline pharmacokinetics were not affected by the co-administration of gemifloxacin. The maximum plasma concentration (C(max)) for theophylline ranged from 8.12 to 17.71 mg/l and from 8. 79 to 16.35 mg/l during concomitant administration with gemifloxacin and placebo, respectively. The corresponding ranges of the area under the plasma concentration-time curve from time zero to the last quantifiable plasma concentration (AUC((0-12))) were 84.6-177.5 mg. h/l and 94.8-165.1 mg.h/l during gemifloxacin and placebo administration, respectively. The point estimates (90% confidence intervals) for dose-normalized AUC((0-12)) and C(max) (theophylline + gemifloxacin):(theophylline + placebo) were 0.99 (0.93, 1.05) and 1.02 (0.93, 1.11), respectively, which were entirely within the equivalence range (0.80, 1.25). The co-administration of gemifloxacin and theophylline was well tolerated, with no clinically significant changes seen in vital signs, 12-lead electrocardiogram readings or laboratory parameters. Adverse events were generally transient, mild to moderate in nature and similar during the gemifloxacin and placebo treatment periods. In conclusion, theophylline and gemifloxacin may be co-administered without any adjustment in theophylline dose.

Evaluation of phototoxic potential of gemifloxacin in healthy volunteers compared with ciprofloxacin

This double-blind, randomized, parallel-group comparative study investigated the phototoxic potential of gemifloxacin mesylate, a potent, novel fluoroquinolone antimicrobial. Forty healthy male and female volunteers received repeat dosing for 7 days with 160 mg or 320 mg of gemifloxacin (o.d., p.m.), 500 mg of ciprofloxacin (b.d.) or placebo (b.d.). On day 5 (large step) and day 6 (small step), graded series of wavebands were irradiated onto the back of each volunteer (phototesting). Skin reactions were assessed 0-30 min (immediate erythema) and 24 and 48 h (delayed erythema) after irradiation. Both gemifloxacin, 320 mg o.d., and ciprofloxacin, 500 mg b.d., were associated with mild phototoxicity following 7 days of administration. The range of mean phototoxic indices (the ratio of minimal erythemal dose at baseline compared with that on day 7 at the end of dosing) was 1.00-2.19 for gemifloxacin and 0.97-2.23 for ciprofloxacin. The abnormal responses occurred within the ultraviolet A region (335-365 +/-30 nm) and were maximal at 24 h. Susceptibility to phototoxicity had cleared 48 h after stopping the drug. The phototoxicity observed with gemifloxacin, 160 mg o.d., was lower than that at the higher dose and similar to that of placebo, suggesting that gemifloxacin phototoxicity is dose dependent. There were no clinically important changes in the safety profiles of gemifloxacin and ciprofloxacin compared with placebo in healthy volunteers after 7 days of repeat dosing. This study demonstrated that gemifloxacin, 320 mg o.d. given for 7 days, has a low potential to cause mild photosensitivity which is similar to that of ciprofloxacin, 500 mg b.d., given for the same period.

Lack of effect of gemifloxacin on the steady-state pharmacodynamics of warfarin in healthy volunteers

Gemifloxacin is a novel fluoroquinolone with a broad spectrum of activity. This double-blind, randomized, parallel-group study was designed to demonstrate the lack of effect of steady-state concentrations of gemifloxacin on the pharmacodynamic effects of warfarin. Healthy male subjects received loading doses of warfarin on days 1 and 2. The warfarin dose was freely titrated until day 10, with the aim of achieving a stable international normalized ratio (INR) for prothrombin time within the range 1.3-1.8 by day 14. On days 14-24 the dose of warfarin was fixed. On days 18-24, subjects also received 320 mg of gemifloxacin or matched placebo, once daily. Thirty-five subjects entered into and completed the co-administration phase of the study. The mean (standard deviation) baseline INR (mean of days 16-18) and INR for day 24 for gemifloxacin plus warfarin were 1.52 (0.12) and 1.46 (0.15), respectively. Corresponding values for placebo plus warfarin were 1. 46 (0.11) and 1.42 (0.17). The point estimate (90% confidence interval) for the difference in day 24 INR, adjusted for baseline, between gemifloxacin and placebo was 0.02 (-0.08, 0.12), which translates to an INR (relative to placebo least squares mean of 1.43) of 1.02 (0.95, 1.09). The 90% confidence interval for the difference in INR between the gemifloxacin and placebo groups was completely contained within the 25% equivalence range. There were no changes of clinical significance in vital signs, 12-lead electrocardiogram readings or laboratory parameters for any subject during the co-administration phase of the study, and no adverse experiences relating to coagulation were reported during this period. It is concluded that the pharmacodynamic effects of warfarin are not affected by gemifloxacin, and therefore both drugs can be co-administered without dosage adjustment.

Coregistration imaging of the foot

We describe a new technique, known as coregistration imaging, which superimposes 99mTc isotope bone scans on to plain radiographs.

We used the technique selectively in cases in which the nuclear medicine physician, who reported the isotope scan, had difficulty in localising the anatomical site of the abnormality.

In the forefoot, coregistration of isotope scans did not help to localise pathology; the scan alone gave sufficient detail.

In 17 patients with pain in the hind- and midfoot, isotope scanning identified eight sites of abnormality in those with normal radiographs. In those with more than one abnormality on plain radiographs the isotope scan eliminated 12 sites of suspicion. Coregistration of the images significantly increased the certainty of localisation of disease (p < 0.001).

We recommend the selective use of coregistration scanning as a useful technique for investigating patients with pain in the foot and ankle.

Coregistration imaging of the foot. A new localisation technique

We describe a new technique, known as coregistration imaging, which superimposes 99mTc isotope bone scans on to plain radiographs. We used the technique selectively in cases in which the nuclear medicine physician, who reported the isotope scan, had difficulty in localising the anatomical site of the abnormality. In the forefoot, coregistration of isotope scans did not help to localise pathology; the scan alone gave sufficient detail. In 17 patients with pain in the hind- and midfoot, isotope scanning identified eight sites of abnormality in those with normal radiographs. In those with more than one abnormality on plain radiographs the isotope scan eliminated 12 sites of suspicion. Coregistration of the images significantly increased the certainty of localisation of disease (p < 0.001). We recommend the selective use of coregistration scanning as a useful technique for investigating patients with pain in the foot and ankle.

Handling of 5-hydroxytryptamine by platelets in migraine

There is little dispute that a link exists between 5-hydroxytryptamine (5HT) and migraine but the exact mechanism of an attack has yet to be established. The handling of 5HT by the platelet is regarded as a simple model of the handling of 5HT by nerve terminals. If differences are seen in how the platelets from migraineurs handle 5HT compared to those from a control population, it is possible that a similar difference exists in the nerve terminal. The Haemostatometer allows the rapid and simultaneous in vitro assessment of platelet function (shear-induced haemostasis), coagulation and thrombolysis from non anticoagulated blood samples. In this study, a baseline comparison of haemostasis was made on 20 migraineurs between attacks and 20 controls. No differences were found in the results from each of the two groups. 5 microM of 5HT was then added to blood taken from 10 migraineurs and 10 controls and the recordings were repeated. Again, no differences were found between the results from the two groups. In blood taken from both migraineurs and controls, the effect of 5HT was to significantly enhance clotting time and clot lysis. No effect was seen on primary aggregation. The possible reasons for and significance of these findings is discussed.

Use of an ammonia electrode for rapid quantification of Helicobacter pylori urease: its use in the endoscopy room and in the assessment of urease inhibition by bismuth subsalicylate

The use of an ammonia electrode to quantify ammonia liberated by urease from Helicobacter pylori was assessed in an in vitro study. It was found to be highly sensitive (down to 0.7 ppm NH3) and highly reproducible (coefficient of variation 6.0%). Inhibition of urease by bismuth subsalicylate was evaluated as urease testing is often used to assess clearance of H. pylori in patients treated with bismuth. Concentrations of bismuth subsalicylate up to 5 mg/ml had no inhibitory effect but bismuth subsalicylate at 50 mg/ml resulted in 21% inhibition of the urease activity of an ultrasonicated H. pylori suspension. As a preliminary study, the ammonia electrode was assessed in the endoscopy room in comparison with conventional techniques for H. pylori diagnosis. Antral biopsies from 39 patients attending for routine diagnostic endoscopy were subjected to culture, histology, detection of urease activity with a commercially available slide test (CLO) and with the ammonia electrode to detect ammonia liberated from samples placed in urea solution. 21 patients were positive after 1 h with the ammonia electrode, compared to only 17 with the commercially available slide test. 20 were positive on histology and 19 by culture. All samples positive with the ammonia electrode were either positive by culture or by histology. The ammonia electrode offers a quick, sensitive, quantitative and cheap method for the detection and quantification of H. pylori.

Ice cream headache--site, duration, and relationship to migraine

OBJECTIVE

To examine the characteristics of cold-induced headaches in a group of migraine patients, to compare these with their usual migraine headaches and with cold-induced headaches in a control population.

DESIGN

Subjects completed a structured questionnaire recording previous headache history along with the characteristics of any headache produced during supervised palatal and pharyngeal application of ice cream.

SUBJECTS

70 consecutive patients attending the City of London Migraine Clinic, and 50 pre-clinical medical and dental student volunteers from Queen Mary and Westfield College.

RESULTS

27% of the migraine patients and 40% of the students reported previous ice cream headaches. 17% of the migraine patients and 46% of the students developed headache following palatal application or a swallow of ice cream. Typically the headache was of early onset (x = 12.5s) and short duration (x = 21s), with a tendency for anterior headache on the same side as a palatal stimulus, and bilateral headache following an ice cream swallow. However, a significant minority experienced a previously unreported headache of late onset (x = 102s) and long duration (x = 236s) which tended to occur particularly after swallowing ice cream and to be less well localised to the side of the cold stimulus. Ice cream appeared not to be a common trigger for migraine, and there was no significant correlation between site of ice cream headache and usual site of migraine.

CONCLUSIONS

These findings confirm that cold stimulation of the palate or pharynx commonly produces a headache. In contrast to previous studies, our results suggest that the 'ice cream headache' is less common in migraine patients than the general population. A similar pattern of headache was produced in both migraine patients and controls, and apart from the few for whom an ice cream headache may trigger a migraine, the ice cream headache seems not to have any special significance for migraine patients.

Studies on Gracilaria. 5. In vitro life history of Gracilaria sp. from the Maritime Provinces

The life history of Gracilaria sp. was completed in culture demonstrating a typical Polysiphonia-type life history. Carpospores released by plants collected in nature developed into tetrasporophytes and subsequent release and germination of tetraspores gave rise to a gametophytic generation morphologically similar to the tetrasporophyte. Development of tetrasporophytes from carpospores released by the carposporophytic generation completed the life history. A male to female ratio of 1:1 was found for plants originating from tetraspores and only female plants grown in the presence of male plants formed fertile cystocarps. Detached plants showed the greatest reproductive potential; reproductive maturation of these plants occurred in 8–10 weeks after spore germination. Vegetative propagation through rapid regeneration of adventitious branches from wound tissue was observed.