Antimicrobial Efficacy of Different Irrigant Solutions Using a Novel Biofilm Model: An In Vitro Confocal Laser Scanning Microscopy Experiment

AIM

To determine the ability of different irrigation solutions to biomechanically remove Enterococcus faecalis biofilm from a novel artificial root canal model during chemomechanical preparation.

METHODS

High resolution micro-computer-tomography scans of a mandibular molar's mesial root were used to produce 50 identical 3D-printed resin root canal models. These were cultured with E.faecalis over seven days to generate biofilm and subjected to chemomechanical preparation using: saline; 17% ethylenediaminetetraacetic acid (EDTA) or 2% sodium hypochlorite (NaOCl) alongside positive/negative controls (n = 10). Canals were prepared to 40/.06 taper, with 1 mL irrigation between instruments, followed by 5 mL penultimate rinse, 30 s ultrasonic activation and 5 mL final rinse. Residual biofilm volume (pixels) was determined following immunofluorescent staining and confocal-laser-scanning-microscopy imaging. Statistical comparisons were made using Kruskal-Wallis with post-hoc Dunn's tests (α ⟨0.05).

RESULTS

In all canal thirds, the greatest biofilm removal was observed with NaOCl, followed by EDTA and saline. The latter had significantly higher E.faecalis counts than NaOCl and EDTA (P ⟨0.01). However, no statistical differences were found between EDTA and NaOCl or saline and positive controls (P ⟩0.05).

CONCLUSIONS

Within limitations of this model, 17% EDTA was found to be as effective as 2% NaOCl at eradicating E.faecalis biofilm following chemomechanical preparation. Further investigations with multi-species biofilms are encouraged.

Curriculum content and assessment of pre-clinical dental skills: A survey of undergraduate dental education in Europe

INTRODUCTION

Since 1981, the qualifications for various healthcare professionals across the European Union have enjoyed mutual recognition in accordance with the EU Directive 81/1057/EEC. Whilst the directive includes dental practitioners, it is recognised that significant variation exists in curriculum structure, content and scope of practice across institutions. This article aimed to explore pan-European practice in relation to curriculum content, teaching and learning strategies and assessment of pre-clinical dental skills.

METHOD

A request to complete an online questionnaire, in English, was sent electronically to skills leads at all Association of Dental Education in Europe member schools. The questionnaire collected information in relation to institution and country, regulatory requirements to demonstrate safety, details of specific pre-clinical skills courses, learning materials and teaching staff.

RESULTS

Forty-eight institutions, from 25 European countries responded. Seven countries (n=7, 28%) reported no requirement to demonstrate student operative safety prior to patient treatment. Several core and operative clinical skills are common to the majority of institutions. The most commonly taught core skills related directly to the clinical environment such as cross-infection control and hand washing. The least common were skills that indirectly related to patient care, such as communication skills and working as a team.

CONCLUSION

There are clear differences within European pre-clinical dental education, and greater efforts are needed to demonstrate that all European students are fit to practice before they start treating patients. Learning outcomes, teaching activities and assessment activities of pre-clinical skills should be shared collaboratively to further standardise curricula.

Recommendations for the development of e-modules for the continuing professional development of European dentists

AIMS

To provide evidence-based and peer-reviewed recommendations for the development of dental continuing professional development (CPD) learning e-modules.

METHODS

The present recommendations are consensus recommendations of the DentCPD project team and were informed by a literature research, consultations from e-learning and IT expert, discussions amongst the participants attending a special interest group during the 2012 ADEE meeting, and feedback from the evaluation procedures of the exemplar e-module (as described in a companion paper within this Supplement). The main focus of these recommendations is on the courses and modules organised and offered by dental schools.

RESULTS AND DISCUSSION

E-modules for dental CPD, as well as for other health professionals' continuing education, have been implemented and evaluated for a number of years. Research shows that the development of e-modules is a team process, undertaken by academics, subject experts, pedagogists, IT and web designers, learning technologists and librarians. The e-module must have clear learning objectives (outcomes), addressing the learners' individual needs, and must be visually attractive, relevant, interactive, promoting critical thinking and providing feedback. The text, graphics and animations must support the objectives and enable the learning process by creating an attractive, easy to navigate and interactive electronic environment. Technology is usually a concern for learners and tutors; therefore, it must be kept simple and interoperable within different systems and software. The pedagogical and technological proficiency of educators is of paramount importance, yet remains a challenge in many instances.

CONCLUSIONS

The development of e-courses and modules for dental CPD is an endeavour undertaken by a group of professionals. It must be underpinned by sound pedagogical and e-learning principles and must incorporate elements for effective visual learning and visual design and a simple, consistent technology.

Guidelines for the organisation of continuing professional development activities for the European dentist

AIM

Free movement of dental professionals across the European Union calls for more uniform continuing education in dentistry to ensure up-to-date, high-quality patient care and patient safety. This article provides guidelines for the management and delivery of high-quality continuing professional development (CPD) by European dental schools and other CPD providers.

METHOD

The guidelines are based on an extensive literature inventory, a survey of existing practices (both available as separate publications), discussions during meetings of the Association for Dental Education in Europe in 2011 and 2012 and debate amongst the members of the DentCPD project team representing six dental schools.

RESULTS

On the basis of the literature review, survey and discussions, we recommend that (i) every dentist should be given the opportunity for CPD, (ii) providers should be quality-approved and impartial, (iii) educators should be approved, impartial, suitably trained, and with educational expertise, (iv) the mode of CPD delivery should suit the educational activity, with clear learning objectives or outcomes, (v) effort should be made to assess the learning, (vi) participant feedback should be collected and analysed to inform future developments and (vii) uniform use of the pan-European system of learning credit points (ECTS) should be implemented.

CONCLUSION

Implementation of these guidelines should make dental CPD more transparent to all relevant parties and facilitate the transferability of earned credits across the European Union. It will also enable better quality control within dentistry, resulting in enhanced dental care and ultimately the improvement in patient safety.

The development of an exemplar e-module for the continuing professional development of European dentists

AIM

To present the development of an exemplar e-module for dental continuing professional development (CPD) provided by dental schools and other dental educational providers.

MATERIALS AND METHODS

The exemplar e-module covered the topic of 'Sterilisation and cross-infection control in the dental practice' as this is one of the most recommended topics for dental CPD in Europe. It was developed by a group of topic experts, adult learning and distance learning experts and a technical developer. Major concerns were pedagogy, interoperability, usability and cost reduction. Open-source material was used to reduce the cost of development.

RESULTS

The e-module was pre-piloted in dental practitioners for usability and then evaluated by experts in the field and dental academics through an electronic questionnaire and an online presentation and discussion at the ADEE 2012 Special Interest Group on DentCPD-Lifelong learning. This facilitated refinement before final production. A Creative Commons License was implemented to ensure the developers' rights and facilitate wider distribution and access to CPD providers.

DISCUSSION AND CONCLUSIONS

The e-module was developed according to well-defined pedagogical and technical guidelines for developing e-learning material for adult learners. It was structured to promote self-study by directing learners through their study, promoting interaction with the material, offering explanation and providing feedback. Content validity was ensured by extensive review by experts. The next step would be to expand the evaluation to practising dentists in various countries after relevant translations, and adaptations to local policies have been made.

International peer review in undergraduate dentistry: enhancing reflective practice in an online community of practice

To stimulate and enhance student learning in the areas of global citizenship, critical reflection and e-learning, an online international peer review using a purpose-built web platform, has been developed between international dental schools. Since its inception in 2007, n = 6 dental schools from six different countries have participated with n = 384 dental students engaged in online peer review. Project development was conceptually analysed utilising Lave and Wenger's notion of a community of practice (CoP). Analysis drew on the three core components within the CoP organising framework: domain, community and practice. All three components were evident in building project identity. The domain focused on both curriculum and institutional co-operation. The community was evident for both educators and students. Finally, analysis of practice was found to be significant in terms of sustained interaction and collaboration. Empirical evaluation is recommended as the next phase of project design.

An audit of the diagnostic usefulness of PRL and TSH responses to domperidone and high resolution magnetic resonance imaging of the pituitary in the evaluation of hyperprolactinaemia

BACKGROUND AND OBJECTIVE

The usefulness of dynamic tests of PRL release in determining underlying pathology in hyperprolactinaemic patients is not well recognized by endocrinologists, only 15% of whom routinely perform such tests. High resolution pituitary magnetic resonance imaging (MRI) has become more widely available during the past 5 years and is now generally regarded as the pituitary imaging method of choice. Since few prolactinoma patients are now submitted to surgery, it is important to ascertain the usefulness of these techniques in suggesting a pathological diagnosis.

DESIGN

A 3 year retrospective audit of the information derived from measurement of PRL and TSH responses to the dopamine antagonist domperidone and from high resolution pituitary MRI in patients being investigated for hyperprolactinemia in regional endocrine unit.

PATIENTS

Eighty-four patients (10 male, 74 female) whose investigation of hyperprolactinaemia included a domperidone test and high resolution pituitary MRI. Patients who had domperidone tests performed after pituitary surgery or who did not have pituitary MRI were excluded from the analysis.

MEASUREMENTS

PRL and TSH were measured basally and at 30 and 60 minutes following domperidone (10 mg i.v.) and gadolinium-enhanced pituitary MRI was performed in all patients.

RESULTS

20 patients had a normal PRL response to domperidone (defined as PRL30/PRL0 > 3) and this group included five patients in whom hyperprolactinaemia was not sustained. Pituitary MRI showed evidence of a microadenoma in only two patients, imaging being unequivocally normal in the majority. Sixty-four patients had an abnormal PRL response to domperidone and 18 of these had a macrolesion (nine prolactinomas, nine other tumours). Pituitary MRI was performed in the remaining 46 patients with abnormal PRL response to domperidone and suggested microadenoma in 29 (63%), identified other structural abnormalities in six cases but was entirely normal in 11 cases. Neither the basal PRL level nor the TSH response could refine the diagnosis further because of overlap between the various subgroups.

CONCLUSIONS

The majority of patients with a normal dynamic response of PRL to domperidone had a normal or near normal pituitary MRI scan. In the two cases where an abnormality was detected it could have been an incidental microadenoma or cyst, thus suggesting that pituitary scanning could normally be omitted in patients whose PRL response to domperidone is normal (24% of our total). The group of patients with an abnormal dynamic response of PRL to domperidone was not generally amenable to further diagnostic refinement by considering the degree of hyperprolactinaemia or the TSH response to domperidone because of overlap of these parameters between the diagnostic subgroups. Therefore any degree of hyperprolactinaemia associated with a blunted PRL response to domperidone warrants pituitary imaging.

Laparoscopic trans-peritoneal adrenalectomy: a preliminary report of 14 adrenalectomies

OBJECTIVES

Laparoscopic adrenalectomy offers the potential benefits of a smaller operation with more rapid hospital discharge, compared to open surgery. Only a few small series have been reported so far. We describe our preliminary experience of 14 adrenalectomies using this new technique.

DESIGN

Review of all adrenalectomies (with the preoperative intention of laparoscopic removal) performed in an endocrine unit whose surgeon already had abdominal laparoscopic experience, particularly with cholecystectomy.

PATIENTS AND MEASUREMENTS

Twelve patients (3 with Conn's syndrome, 3 Cushing's syndrome, 1 Cushing's disease, 2 phaeochromocytomas and 3 adrenal incidentalomas) were operated between September 1993 and February 1996. Operating times, operative technique, time from surgery to discharge, outcome and all complications were recorded prospectively. Comparative data were obtained from 14 consecutive open adrenalectomies performed by the same surgeon between February 1989 and February 1995.

RESULTS

Fourteen glands were removed, two with a cholecystectomy, in 12 operations. Operating time (mean (range) 120 (60-225) min) was reduced with experience. Positioning the patient in the right lateral position facilitated left adrenalectomy. Time to discharge (mean (range)) was 5.3 (1-12) days. There were relatively minor complications in three patients, including two with Cushing's syndrome: a hernia at a port site, intra-peritoneal/wound haemorrhage and a pressure sore. Time to discharge for open adrenalectomy (mean (range)) was 6.5 (2-11) days and one case was complicated by wound infection.

CONCLUSIONS

Laparoscopic adrenalectomy is a practical technique for appropriately trained surgeons who regularly undertake adrenalectomy. The smaller incisions offer potential advantages, particularly for patients with poor tissue quality due to Cushing's syndrome, but tissue haemorrhage may still be a problem in these patients. Time to hospital discharge was similar to that for open surgery.

Aggressive limb salvage using tibio-pedal bypass grafting with free tissue transfer in a diabetic patient

A 63-year-old man presented with intermittent claudication, diabetes, and an ischaemic heel ulcer. After control of infection, the os calcis was left exposed. An aggressive combined infra-inguinal revascularization and reconstruction procedure involving free-tissue transfer resulted in rapid wound healing with independent walking by day 26. Recent improvements in surgical techniques mean that this approach should be considered in selected patients.

Nesidioblastosis in an elderly patient

We report an 84-year-old woman with hypoglycaemia and hyperinsulinaemia caused by diffuse nesidioblastosis. This is the oldest case of nesidioblastosis so far recorded. The case illustrates some of the difficulties in diagnosing inappropriate hyperinsulinaemia and the benefits of surgery, even in old age. Hypoglycaemia should be considered in patients with variable mental function.

The degree of day-to-day variation in food intake in diabetic patients

A prospective study of food intake using 7 day food diaries was undertaken in 92 diabetic men and women aged 17-81 years. The median individual day-to-day coefficients of variation for energy intake were: in insulin treated patients 12.0%, in non-insulin treated patients 13.7%; for carbohydrate intake 14.5% and 13.8% and for fat 20.7% and 20.8%, respectively. The median individual differences between the minimum and maximum daily intake of energy in insulin treated patients was 787 kcal, in non-insulin treated patients 649 kcal, for carbohydrate intake 89g and 77g and fat 50g and 43g, respectively. Only 39% patients ate within 20% of their prescribed carbohydrate diet. In non-insulin treated patients on prescribed calorie controlled diets, calorie consumption was on average 46% in excess of that prescribed. Although the variation in dietary intake in diabetic patients is large, it is smaller than that reported in non-diabetic subjects in the UK. This variation is likely to make the manipulation of other antidiabetic therapy both difficult and somewhat arbitrary.

Generation of thrombin activity in relation to factor VIII:C concentrations and vascular complications in type 1 (insulin-dependent) diabetes mellitus

A possible association between plasma coagulant activity and the presence of vascular complications in patients with diabetes mellitus was studied by measuring the generation of thrombin in plasma of 20 control subjects and 50 diabetic patients classified according to the presence or absence of microvascular complications. Thrombin production was determined in defibrinated plasma using a semi-automated technique with measurement of thrombin activity using chromogenic peptide S2238. Values determined were the lag time to appearance of thrombin activity and time taken to generate 50% maximal thrombin activity. Thrombin activity was related to concentrations of coagulant factor VIII activity and fibrinopeptide A and these were correlated with HbA1C levels. The median time to generate 50% maximal thrombin activity was not significantly reduced in diabetic patients compared with control subjects (53 vs 54 s, p = 0.076) and there were no significant differences between patients with and without microvascular complications. There were no differences in median fibrinopeptide A concentrations between the diabetic and control subjects (1.5 vs 2.2 nmol/l, p = 0.169). Time to 50% maximal thrombin activity correlated inversely with factor VIII:C concentrations in diabetic patients (r = -0.344, p = 0.015, n = 50) and both this and lag time correlated with factor VIII:C in diabetic patients and control subjects combined (r = -0.395, p less than 0.01; r = -0.327, p = 0.006, n = 70). Factor VIII:C concentrations increased with age of the subject and with HbA1C concentrations. The results failed to show enhancement of coagulation in contact-activated diabetic plasma compared with control plasma and suggest that a relationship between high levels of factor VIII:C in diabetes and the development of mcirovascular complications is unlikely to be mediated through procoagulant activity in plasma.

Diabetic diets and nutritional recommendations: what happens in real life?

Prospective 7-day estimated weight food records were computer analysed in 92 diabetic patients, 45 men and 47 women, 25 with Type 1 and 67 Type 2 diabetes, attending a hospital-based diabetic clinic. The nutrient intakes were compared with a national survey in non-diabetic British adults (OPCS) and the current EASD recommendations for the diabetic diet. Only three diabetic patients achieved the recommended 50-60% energy intake as carbohydrate, four achieved less than 30% energy as fat, one patient less than 10% saturated fat and 20 ate greater than 30 g fibre per day. The overall nutrient intakes of these diabetic patients reflected those of non-diabetic subjects except for a greater intake of protein and smaller intakes of sugar and alcohol. These findings reinforce the problems currently faced in achieving the present recommendations for the diabetic diet.

Contrasting fibrinolytic responses in type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes

To study fibrinolysis in relation to microvascular diabetic complications, 20 control subjects were compared with 50 Type 1 (insulin-dependent) diabetic patients of similar age, 20 with no complications, 17 with laser-treated retinopathy, and 13 with neuropathy and retinopathy. None were smokers, hypertensive or had macrovascular disease. Pre- and post-venous occlusion blood samples for tests of fibrinolysis were taken. Median (interquartile range) basal tissue plasminogen activator (t-PA) activity was lower in control subjects (100 (less than 100-100) IU l-1) than diabetic patients (uncomplicated 145 (100-280) IU l-1, p = 0.015; retinopathy 180 (100-228) IU l-1, p = 0.037; neuropathy 210 (125-310) IU l-1, p = 0.004, respectively). Basal t-PA inhibition (PAl-1 activity) was higher in control subjects (5.9 (4.5-9.5) kIU l-1) than diabetic patients (uncomplicated 4.0 (3.3-5.0) kIU l-1, p = 0.001; retinopathy 4.5 (3.1-6.3) kIU l-1, p = 0.058; neuropathy 4.0 (3.0-5.4) kIU l-1, p = 0.015, respectively). Post-venous occlusion t-PA antigen was higher in control subjects (10.2 (7.3-15.1) micrograms l-1) than neuropathic patients (5.5 (4.9-7.3) micrograms l-1, p = 0.004). Other tests showed a consistent, but non-significant, trend towards increased basal fibrinolysis in the Type 1 diabetic patients. The results indicate that Type 1 diabetic patients have enhanced basal fibrinolysis. The diminished response to venous occlusion in neuropathic patients is consistent with an endothelial cell defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Early loss of neurogenic inflammation in the human diabetic foot

1. Neurogenic inflammation, mediated by nociceptor C fibres, is part of the acute neurovascular response to injury producing the axon reflex flare. Laser Doppler flowmetry was used to measure the flare response induced by the electrophoresis, at various current strengths, of a ring of acetylcholine solution into dorsal foot skin. 2. Nineteen control subjects and 52 long-duration insulin-dependent (Type 1) diabetic patients of similar age (20 without complications; 19 with laser-treated retinopathy; 13 with reduced vibration perception and retinopathy) were studied in order to investigate the possible attenuation of this defence mechanism in diabetes. 3. The maximal (1 mA) flare response [control median (interquartile range): 1.55 (1.16-2.06) arbitrary units] was reduced greatly in neuropathic patients [0.37 (0.24-0.66) arbitrary units; P less than or equal to 0.001 with respect to all other groups], especially those with a previous history of foot ulceration. The flare was also reduced in some patients with retinopathy alone [1.06 (0.56-1.27) arbitrary units; P less than 0.005 with respect to control subjects]. 4. No rightward shift of the curve of hyperaemic response plotted against current strength was found, suggesting that the abnormal response was due to axonal loss rather than to dysfunction. 5. Neurogenic inflammation, mediated by small pain fibres, was markedly impaired in a group of diabetic patients at risk of foot ulceration. Furthermore, impairment of this nociceptor C fibre response can develop before clinical large-fibre neuropathy and could itself predispose to foot complications.

Assessment of the neurogenic flare response as a measure of nociceptor C fibre function

A modified method for quantitative measurement of nociceptor C fibre function is described. The electrophoresis of acetylcholine stimulates C fibres to produce an axon reflex flare which is measured by laser Doppler flowmetry. The use of the dorsal, rather than the plantar, surface of the foot at a skin temperature of 32-33 degrees C rather than 34-35 degrees C improves the sensitivity of the technique. Acetylcholine produces an earlier and more predictable response than normal saline, which is approximately half maximal at a current of 0.2 mA and maximal at 1.0 mA. The use of different current strengths should allow more detailed assessment of neurogenic inflammation and the effects of drugs and disease states on C fibre function.

Evidence for an abnormal peripherally mediated vascular response to temperature in Raynaud's phenomenon

It is unclear whether an abnormal vascular response to temperature change, independent of central sympathetic control, exists in Raynaud's phenomenon. We investigated this using the hyperaemic response to localized heating of dorsal foot skin, recorded by laser Doppler flowmetry. Fifteen normal adults, nine patients with primary, and seven with secondary Raynaud's phenomenon were studied. On warming, blood flow normally increases gradually at first, followed by rapid vasodilatation at temperatures above 33 degrees C. Normal geometric mean (95% confidence interval) blood flows at 33 degrees C and 36 degrees C were 0.19 (0.16-0.22) and 0.39 (0.29-0.53) arbitrary units respectively. In primary Raynaud's phenomenon, blood flows were 0.53 (0.44-0.62) and 1.07 (0.86-1.35) arbitrary units respectively (P less than 0.01 compared to normal subjects), showing early vasodilatation. Normal women have an intermediate response between men and primary Raynaud's patients. Responses in secondary Raynaud's phenomenon widely overlap the other groups. We conclude that an abnormal peripheral vascular response to temperature change exists in primary Raynaud's phenomenon.

Myogenic microvascular responses are impaired in long-duration type 1 diabetes

Post-ischaemic hyperaemia is a complex physiological response. Peak flow is predominantly an arteriolar myogenic response, whilst viscoelasticity of supplying arteries determines speed of vasodilatation. Impaired post-ischaemic hyperaemia has been described in neuropathic diabetic feet and might predispose to ulceration. However, the relationships of myogenic response and vasodilatation to diabetic control and microvascular complications are unclear. These relationships were therefore investigated using laser Doppler flowmetry to measure the hyperaemic response on the dorsum of the foot after 10 min ischaemia. Twenty control subjects were compared with 55 long-duration Type 1 diabetic patients in groups of uncomplicated, retinopathic and neuropathic patients. Peak flow (median (interquartile range)) was reduced from 1.40 (1.20-1.61) in control subjects to 1.15 (0.80-1.29), 1.08 (0.75-1.26), and 0.95 (0.62-1.29) arbitrary units in the diabetic groups respectively (p = 0.012-0.004). Time to half peak flow was shorter in neuropathic diabetic patients compared with all other groups: 9.5 (7-19), 14.5 (5-25), 12.5 (6-20), and 4 (3-6) s, respectively (p = 0.027-0.011). Neuropathic patients also had the steepest initial slope of vasodilatation. Thus, in long-duration diabetic patients, the myogenic peak post-ischaemic hyperaemic response is impaired, but this impairment is not specifically associated with microvascular complications and was not related to recent blood glucose control. The shortened time to half peak flow and rapid vasodilatation in neuropathic patients is likely to reflect increased rigidity of their arteries.

Reduced hyperaemia following skin trauma: evidence for an impaired microvascular response to injury in the diabetic foot

The hyperaemic response to standard needle injury within dorsal foot skin was investigated in normal and Type 1 (insulin-dependent) diabetic subjects using laser Doppler flowmetry. The normal response was maximal within 15 min, localised, prolonged and biphasic. In 20 normal subjects and three groups of long-duration Type 1 diabetic patients (20 without complications; 20 with laser-treated retinopathy; 15 with neuropathy and retinopathy), the median (interquartile range) peak hyperaemic responses were 1.766 (1.220-1.970), 1.485 (1.342-1.672), 0.997 (0.705-1.203) and 1.030 (0.718-1.369) arbitrary units, respectively. Compared to normal and uncomplicated diabetic groups, peak flow was significantly reduced in the retinopathic (p less than 0.0001) and neuropathic (p = 0.001 and 0.007, respectively) groups. There was no significant difference between the normal and uncomplicated diabetic groups, nor between the retinopathic and neuropathic groups. There was no association of the hyperaemic response with blood sugar, HbA1c, or duration of diabetes. Diabetic patients who have microvascular complications, with or without neuropathy, have an associated impairment of microvascular response to mechanical injury which might predispose to infection and poor wound healing.

31P nuclear magnetic resonance measurement of free erythrocyte magnesium concentration in man and its relation to blood pressure

1. 31P n.m.r. spectroscopy was used to measure the dissociation constant of MgATP under simulated intracellular conditions and to measure erythrocyte free magnesium concentration. 2. In a group of 40 subjects, the relationship between erythrocyte free magnesium and blood pressure, age and sex was examined by univariate and multivariate regression analysis. 3. A weak positive association was found between erythrocyte free magnesium and mean blood pressure. This association was lost in a multivariate regression analysis including both age and sex. 4. No significant relationship was found between erythrocyte free magnesium and age, sex, family history of hypertension or use of the combined oral contraceptive pill in the sample studied.

An in vitro pharmacological study of the human trigone--a site of non-adrenergic, non-cholinergic neurotransmission

Muscle strips from the human detrusor and trigone were studied in vitro. The detrusor muscle contracted strongly to both cholinergic receptor stimulation with carbachol and to electrical field stimulation. There was no evidence of atropine resistance in the detrusor strips. The superficial trigone responded maximally to alpha-adrenergic receptor stimulation but also produced a significant cholinergic response. Intramural nerve stimulation in the presence of both atropine and phentolamine produced a residual non-adrenergic, non-cholinergic (NANC) response of 40% of its maximum at 5 Hz. Electrical stimulation, particularly at the lower frequencies of stimulation, produced relaxation responses in 40% of the superficial trigonal muscle strips. These relaxations were not blocked by atropine, phentolamine or propranolol, but were abolished by tetrodotoxin. The possible role of the cholinergic "input" to the superficial trigone and the importance of the NANC excitatory and inhibitory innervation in preventing vesico-ureteric reflux and and in aiding bladder neck opening is discussed.

An investigation of sodium-calcium exchange in the smooth muscle of guinea-pig ureter

1. After application of ouabain (10(-4) M), the intracellular Na+ activity (alpha iNa) of smooth muscle cells in the guinea-pig ureter stabilizes at a relatively low level which can be rapidly lowered by reduction of external Na+ (Na+o) or elevation of Ca2+o. Both these procedures also elicit a transient contracture. These observations have previously been interpreted as evidence for Na+-Ca2+ exchange. The presence of such an exchange mechanism has now been further investigated by measurements of alpha iNa, tension, ion analysis and 22Na efflux. 2. Ion analysis demonstrated that tissues were able to maintain a high cellular K+ content in the presence of ouabain, but slowly lost K+ and gained Na+ if K+o was also removed, as expected for an infinite outward gradient for K+ and a fully inhibited Na+ pump. 3. Tissues were only able to maintain a low cellular Na+ and high cellular K+ in the presence of ouabain if Ca2+ was present in the bathing solution. Reduction of Ca2+o to very low levels also caused a continual slow rise in alpha iNa in the presence of ouabain, provided that the prolonged depolarization caused by these low levels was prevented by elevation of Mg2+o. Alteration of the membrane potential by changing K+o at constant Na+o showed that alpha iNa decreased by about 1.2 mM for a 10 mV depolarization, within the range from -70 to -30 mV. 4. A small Ca2+o-activated 22Na efflux was observed in ouabain-treated tissues in the absence of Na+o. 40 mM-Ca2+ was not more effective at activating this efflux than was 2.5 mM-Ca2+, while 40 mM-Mg2+ was ineffective. Restoration of the normal Na+o caused a large increase in the rate of 22Na loss. 5. Application of Mn2+ in the presence of ouabain caused a slow rise in alpha iNa and a small decline in resting tension. The fall in alpha iNa on reduction of Na+o was slowed by the presence of Mn2+ (mean half-time increased from 1.7 to 5.0 min) and the concomitant contracture was almost abolished. These results are consistent with a Mn2+-induced inhibition of Na+-Ca2+ exchange. However, the fall in alpha iNa induced by elevation of Ca2+o was unaffected by the presence of Mn2+ and the attendant contracture was, if anything, enhanced. 6. Observation of changes in alpha iNa and tension at various Mn2+ and Ca2+ concentrations demonstrated a competitive interaction between the two divalent cations.(ABSTRACT TRUNCATED AT 400 WORDS)