Redescription of Besnoitia bennetti (Protozoa: Apicomplexa) from the donkey (Equus asinus)

Besnoitia bennetti tissue cysts were found in four naturally-infected donkeys (Equus asinus) from the USA. Infectivity of its bradyzoites and tachyzoites to animals and cell culture was studied. The bradyzoites were not infectious to out-bred Swiss Webster mice, rabbits or gerbils. When fed tissue cysts, cats did not excrete oocysts. However, the parasite was infectious to interferon-gamma gene knock out mice. The parasite from tissues of two donkeys was grown successfully in bovine monocyte monolayers for the first time. Non-dividing, uninucleate tachyzoites were approximately 6 x 1.5 microm in size. Longitudinally-cut bradyzoites in tissue sections measured 8.7 x 1.9 microm. Ultrastructurally, tachyzoites and bradyzoites were similar to those in other Besnoitia species, and in particular to parasites described from cattle (Besnoitia besnoiti) and reindeer (Besnoitia tarandi), in that their bradyzoites lacked enigmatic bodies. Based on comparative analysis of three portions of nuclear ribosomal DNA (the small and large subunits and the first internal transcribed spacer) B. bennetti was found to be more closely related to the other congeners described from ungulates. The parasite was formally redescribed and specimens deposited in the US National Parasite Collections.

Evaluation of an MRI-based protocol for cell implantation in four patients with Huntington's disease

The purpose of this study was to evaluate our surgical protocol for the preparation and delivery of suspensions of fetal tissue into the diseased human brain. We implanted suspensions of human fetal striatal anlage into the right caudate and putamen of four patients with Huntington's disease. Postoperative 3 tesla MR imaging confirmed accurate graft placement. Variability in graft survival was noted and the MR signal changes over 6 months revealed persistent hyperintense signal on T2-weighted images. Our results are consistent with those described by other groups and indicate that our surgical protocol is safe, accurate, and reproducible.

Acute ketamine administration alters the brain responses to executive demands in a verbal working memory task: an FMRI study

We have used functional MRI to determine the effects of ketamine on brain systems activated in association with a working memory task. Healthy volunteers received intravenous infusions of placebo, ketamine at 50 ng/ml plasma concentration, and ketamine at 100 ng/ml. They were scanned while carrying out a verbal working memory task in which we varied the executive requirements (manipulation vs maintenance processes) and the mnemonic load (three vs five presented letters). We previously showed that ketamine produces a specific behavioral impairment in the manipulation task. In the current study, we modified tasks in order to match performance across drug and placebo conditions, and used an event-related fMRI design, allowing us to remove unsuccessful trials from the analysis. Our results suggest a task-specific effect of ketamine on working memory in a brain system comprising frontal cortex, parietal cortex, and putamen. When subjects are required to manipulate presented letters into alphabetical order, as opposed to maintaining them in the order in which they were presented, ketamine is associated with significantly greater activity in this system, even under these performance-matched conditions. No significant effect of ketamine was seen in association with increasing load. This suggests that our findings are not explicable in terms of a nonspecific effect of ketamine when task difficulty is increased. Rather, our findings provide evidence that the predominant effects of low, subdissociative doses of ketamine are upon the control processes engaged by the manipulation task. Furthermore, we have shown that ketamine's effects may be elucidated by fMRI even when overt behavioral measures show no evidence of impairment.

USE OF 18FDG-PET TO DISCRIMINATE BETWEEN INFECTION AND REJECTION IN LUNG TRANSPLANT RECIPIENTS

18F-fluorodeoxyglucose (18FDG) uptake measured by positron emission tomography (PET) allows assessment of neutrophil activity in vivo and is increased in patients with airway inflammation or infection. Because infection but not rejection elicits a highly neutrophilic response, we assessed the ability of this non-invasive technique to differentiate these two events in lung transplant recipients. 18FDG-PET was measured in 15 patients classified by clinical, radiologic, and pathologic criteria. 18FDG-PET signal was increased with proven infection but not when no infection was identified (mean [standard error of mean]: 8.00 [1.81] and 3.16 [0.61], respectively [P = 0.021]. Rejection alone did not increase the signal. These data confirm that neutrophil activation is not a feature of acute rejection and indicate that a high 18FDG-PET signal is indicative of infection but not rejection in lung transplant recipients. This non-invasive and repeatable test could reduce the number of transbronchial biopsies required during episodes of breathlessness after lung transplantation.

Detection or decision errors? Missed lung cancer from the posteroanterior chest radiograph

A test bank of verified chest radiographs was compiled for visual search experiments to investigate radiology performance in the detection of early lung cancer. A measure of the physical characteristics of the lesions was derived to determine the conspicuity (chi) of the nodules and to investigate possible causes of failed detection. Observer performance was measured by alternate free response operating characteristic (AFROC) methodology and was supplemented with visual search recording. Correlation of AFROC scores and the chi values was poor but inspection of the visual search recordings showed that most nodules were fixated. Fixations on missed lesions produced average dwell times greater than three times the minimum duration thought to be associated with detection. We conclude that the majority of errors were failures of decision rather than detection and comment on the implications of this for strategies to improve diagnostic effectiveness.

Stereotactic MR imaging for planning neural transplantation: a reliable technique at 3 Tesla?

The purpose of this study was to assess the accuracy of high field (3 Tesla) MR in target localization for stem cell transplantation. Three patients with Huntington's disease were imaged with a stereotactic frame in place for both MRI and CT. Quality assurance procedures and manual shimming were performed before each MRI study to minimize image distortion. The images were fused using multi-modality rigid body image registration software. Image fusion demonstrated the MR images to be in agreement with CT to within 1.5 mm, as assessed by measuring the coordinates of markers on the frame and on the shape and size of the lateral ventricles. Target coordinates for transplantation were selected from the MR images. Postoperative imaging confirmed accurate graft placement.

Long-term oral sensitivity and feeding skills of low-risk pre-term infants

This study examined the oral sensitivity and feeding skills of low-risk pre-term infants at 11-17 months corrected age. Twenty pre-term infants (PT) born between 32 and 37 weeks at birth without any medical comorbidities were assessed. All of this PT group received supplemental nasogastric (NG) tube feeds during their birth-stay in hospital. A matched control group of 10 healthy full-term infants (FT) was also assessed. Oral sensitivity and feeding skills were assessed during a typical mealtime using the Royal Children's Hospital Oral Sensitivity Checklist (OSC) and the Pre-Speech Assessment Scale (PSAS). Results demonstrated that, at 11-17 months corrected age, the PT group displayed significantly more behaviours suggestive of altered oral sensitivity and facial defensiveness, and a trend of more delayed feeding development than the FT group. Further, results demonstrated that, relative to the FT group, pre-term infants who received greater than 3 weeks of NG feeding (PT>3NG) displayed significantly more facial defensive behaviour, and displayed significant delays across more aspects of their feeding development than pre-term infants who received less than 2 weeks of NG feeding (PT<2NG). The information from this preliminary study suggests that low-risk pre-term infants, particularly those who receive supplemental NG feeding for greater than 3 weeks, may be at risk for displaying long-term altered oral sensitivity and facial defensiveness, as well as feeding delays. These observations warrant further investigation on this topic.

Normal pressure hydrocephalus and cerebral blood flow: a PET study of baseline values

Regional cerebral blood flow (CBF) was studied with O(15)-water positron emission tomography and anatomic region-of-interest analysis on co-registered magnetic resonance in patients with idiopathic (n = 12) and secondary (n = 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n = 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH. The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.

Using simulated patients in a multiprofessional communications skills programme: reflections from the programme facilitators

This paper discusses a multiprofessional, 4-day communication skills programme in which participants explore the challenges of communicating with cancer patients and their families. Effective communication and skilled emotional support are essential prerequisites for high quality care in oncology and palliative care settings. This aspect of care presents major challenges to nurses and other health care professionals. It is acknowledged that health professionals often lack the requisite skills to communicate meaningfully with this patient group and that tangible benefits accrue from training in this area. Using simulated patients, structured feedback and small group discussions, this multiprofessional programme seeks to provide a forum that enables participants to acquire confidence and competence in a safe, comfortable and non-threatening environment. The programme structure presents several challenges in terms of providing a learning experience that addresses the diverse educational of a heterogeneous learning group. Participants' comments and programme facilitators reflections suggest that the programme is successful in addressing these challenges and providing a meaningful learning experience.

Cerebrovascular pressure reactivity is related to global cerebral oxygen metabolism after head injury

BACKGROUND

After head injury, impaired cerebrovascular autoregulation has been associated with abnormally high or low cerebral blood flow. The physiological relevance of cerebral blood flow levels is difficult to assess in these patients, whose cerebral metabolic rate for oxygen (CMRO(2)) is known to be abnormal. Investigation of these relations requires quantitative measures of cerebral blood flow and CMRO(2), to allow assessment of oxygen supply and demand relations.

OBJECTIVES

To investigate the relation between dysautoregulation and global cerebral oxygen metabolism following head injury.

METHODS

Using positron emission tomography, global cerebral blood flow, CMRO(2), and oxygen extraction fraction were determined in 22 patients who were investigated in 26 examinations on days 1 to 11 (mean (SD), 3.5 (2.3)) after head injury. Cerebrovascular pressure reactivity was assessed using a pressure reactivity index, calculated as the moving linear correlation coefficient between mean arterial blood pressure and intracranial pressure. Outcome was assessed six months after injury using the Glasgow outcome scale.

RESULTS

Low CMRO(2) was associated with disturbed pressure reactivity (inverse function, R(2) = 0.21, p = 0.018) and there was a correlation between disturbed pressure reactivity and oxygen extraction fraction (quadratic function, R(2) = 0.55, p = 0.0001). There was no significant relation between pressure reactivity and cerebral blood flow. An unfavourable outcome was associated with disturbed pressure reactivity. There was no significant relation between outcome and CMRO(2) or oxygen extraction fraction.

CONCLUSIONS

There is a close relation between dysautoregulation and abnormal cerebral metabolism but not blood flow. Further studies are needed to determine whether metabolic dysfunction is a result of or a cause of disturbed pressure reactivity, and to establish if there is a relation between cerebral oxygen metabolism and outcome.

Diffusion tensor imaging of brain tumours at 3T: a potential tool for assessing white matter tract invasion?

AIM

To determine whether diffusion tensor imaging (DTI) of brain tumours can demonstrate abnormalities distal to hyperintensities on T2-weighted images, and possibly relate these to tumour grade.

MATERIALS AND METHODS

Twenty patients with histologically confirmed supratentorial tumours, both gliomas (high and low grade) and metastases, were imaged at 3T using T2-weighted and DTI sequences. Regions of interest (ROI) were drawn within the tumour, in white matter at various distances from the tumour and in areas of abnormality on DTI that appeared normal on T2-weighted images. The relative anisotropy index (RAI)-a measure of white matter organization, was calculated for these ROI.

RESULTS

The abnormality on DTI was larger than that seen on T2-weighted images in 10/13 patients (77%) with high-grade gliomas. New abnormalities were seen in the contralateral white matter in 4/13 (30%) of these cases. In these high-grade tumours the RAI in areas of white matter disruption with normal appearance on T2-weighted images was reduced (0.19+/-0.04). Even excluding patients with previous radiotherapy this difference remains significant. In all non high-grade tumours (WHO grade II gliomas and metastases) the tumour extent on DTI was identical to the abnormalities shown on T2-weighted imaging and RAI measurements were not reduced (0.3+/-0.04).

CONCLUSIONS

Subtle white matter disruption can be identified using DTI in patients with high-grade gliomas. Such disruption is not identified in association with metastases or low-grade gliomas despite these tumours producing significant mass effect and oedema. We suggest the changes in DTI may be due to tumour infiltration and that the DTI may provide a useful method of detecting occult white matter invasion by gliomas.

The sacroiliac joints: evaluation using nuclear scintigraphy. Part 1: The normal horse

REASONS FOR PERFORMING STUDY

Sacroiliac (SI) disease is recognised as a cause of poor hindlimb action but differential diagnosis is often difficult.

HYPOTHESES

That in clinically normal horses there would be a significant difference in the ratio of radiopharmaceutical uptake (RU) between the fifth lumbar vertebra (L5) and each tuber sacrale (TS) and between L5 and each SI joint; and that these ratios would alter with age, but ratios would be bilaterally symmetrical.

METHODS

Dorsal scintigraphic images of the SI region of 15 horses, selected randomly from the clinic database, were analysed by 2 of the authors, comparing noncorrected and motion-corrected images. To determine scintigraphic anatomy, the scintigraphic images of 10 Thoroughbred horses were superimposed over a ventrodorsal radiographic image of an isolated pelvis. Dorsal scintigraphic images of 40 clinically normal horses age 3-16 years were evaluated using subjective examination, profile analysis and quantification using regions of interest.

RESULTS

The tubera sacrale were seen as 2 well-defined oval regions immediately to the left and right of the midline, abaxial to which were larger, approximately oval areas with less RU, representing uptake in the SI joints. The definition between the SI region and the TS was more obvious in younger horses. Nonmotion-corrected images were often not of diagnostic quality or could be misinterpreted as abnormal. There were significant differences in RU between the TS and SI joints compared to L5, and decreased RU in the tubera sacrale with increasing age, but no change of uptake in the SI joint region and no effect of gender on RU. There was a high degree of left-right symmetry of the TS and SI joint regions.

CONCLUSIONS AND POTENTIAL RELEVANCE

The scintigraphic images of horses with suspected sacroiliac joint disease should be compared with images of normal horses of comparable age. In normal horses, there was a high degree of symmetry; therefore, marked left-right asymmetry is likely to be abnormal.

Assessment of the Ventrix parenchymal intracranial pressure monitoring probe (NL950-P) and Monitor (NL950-100) in a 3 Tesla magnetic resonance scanner

Magnetic resonance (MR) imaging and spectroscopy provide important information in patients with acute head injury. However, optimal patient management requires intracranial pressure (ICP) monitoring. There are few reports on the use of ICP sensors in an MR environment. We tested the Ventrix parenchymal intracranial pressure monitoring probe and monitor (Integra Neurosciences, USA), modified by the use of a fibre-optic extension cable, within a 3 Tesla MR system. The device performed well in the MR environment, but one element within the fibre-optic extension was significantly ferromagnetic. The ICP probe produced a small susceptibility artefact on spin echo images, and a larger artefact on gradient echo images. The MR safety of the integrated system is probably acceptable, but could be easily improved with minor modifications. Although the system is MR compatible and produces generally acceptable imaging even at 3 Tesla, there is significant degradation of image quality during gradient echo sequences.

A resurgence of congenital rubella in Australia?

Two infants with congenital rubella defects (congenital rubella syndrome) have been reported from Queensland in 2003, after an increase in rubella in that State in 2001-2002. The national Measles Control Campaign in 1998 aimed to give measles-mumps-rubella (MMR) vaccine to all unvaccinated preschoolers and a second dose to primary schoolchildren. Following the Campaign no children with congenital rubella defects were born to Australian-born mothers during the five years 1998 to 2002, according to reports to the Australian Paediatric Surveillance Unit. However, three imported cases occurred. Broad immunisation coverage and detection and vaccination of susceptible women of child-bearing age before they become pregnant are necessary to prevent further cases.

Effect of hyperventilation on cerebral blood flow in traumatic head injury: clinical relevance and monitoring correlates

OBJECTIVE

To investigate the effect of hyperventilation on cerebral blood flow in traumatic brain injury.

DESIGN

A prospective interventional study.

SETTING

A specialist neurocritical care unit.

PATIENTS

Fourteen healthy volunteers and 33 patients within 7 days of closed head injury.

INTERVENTIONS

All subjects underwent positron emission tomography imaging of cerebral blood flow. In patients, PaCO2 was reduced from 36 +/- 1 to 29 +/- 1 torr (4.8 +/- 0.1 to 3.9 +/- 0.1 kPa) and measurements repeated. Jugular venous saturation (SjvO2 ) and arteriovenous oxygen content differences (AVDO2 ) were monitored in 25 patients and values related to positron emission tomography variables.

MEASUREMENTS AND MAIN RESULTS

The volumes of critically hypoperfused and hyperperfused brain (HypoBV and HyperBV, in milliliters) were calculated based on thresholds of 10 and 55 mL.100g(-1).min(-1), respectively. Whereas baseline HypoBV was significantly higher in patients ( p<.05), baseline HyperBV was similar to values in healthy volunteers. Hyperventilation resulted in increases in cerebral perfusion pressure (p <.0001) and reductions in intracranial pressure (p <.001), whereas SjvO2 (>50%) and AVDO2 (<9 mL/mL) did not exceed global ischemic thresholds. However, despite these beneficial effects, hyperventilation shifted the cerebral blood flow distribution curve toward the hypoperfused range, with a decrease in global cerebral blood flow (31 +/- 1 to 23 +/- 1 mL.100g(-1).min(-1); p<.0001) and an increase in HypoBV (22 [1-141] to 51 [2-428] mL; p<.0001). Hyperventilation-induced increases in HypoBV were apparently nonlinear, with a threshold value between 34 and 38 torr (4.5-5 kPa).

CONCLUSIONS

Hyperventilation increases the volume of severely hypoperfused tissue within the injured brain, despite improvements in cerebral perfusion pressure and intracranial pressure. Significant hyperperfusion is uncommon, even at a time when conventional clinical management includes a role for modest hyperventilation. These reductions in regional cerebral perfusion are not associated with ischemia, as defined by global monitors of oxygenation, but may represent regions of potentially ischemic brain tissue.

Assessment of the Caradyne WhisperFlow for administration of continuous positive airway pressure in a 3 Tesla magnetic resonance scanner

Demand for magnetic resonance investigations in critically ill patients is increasing. While these patients frequently need ventilatory support, not all of them require controlled ventilation and many may be treated with continuous positive airway pressure. Controlled ventilation, with the concurrent need for sedation, may be inappropriate when airway physiology is being studied and may retard weaning. No commercially available ventilator designed for the magnetic resonance environment can deliver high flow continuous positive airway pressure. We tested the Caradyne Whisperflow flow generator and five Whisperflow valves (2.5-15 cmH2O airway pressure) within a 3 Tesla environment for safety and possible dysfunction. All components had minimal ferromagnetic properties and tests showed no clinically relevant change in flow delivery or oxygen concentration in the magnetic field. In addition, the airway pressure generated by the valves was not affected by the magnetic field. We conclude that the tested system can be safely used in a 3 Tesla magnetic resonance environment.

Cerebral autoregulation among patients with symptoms of hydrocephalus

OBJECTIVE

To study the relationship between the resistance to cerebrospinal fluid (CSF) outflow and cerebral autoregulation.

METHODS

We examined 35 patients who presented with ventricular dilation and clinical symptoms of communicating hydrocephalus. For all of these patients, CSF compensatory reserve was investigated by using a computerized infusion test, with simultaneous recording of blood flow velocity wave forms (by using transcranial Doppler ultrasonography) and arterial blood pressure (with a Finapress finger cuff). The resistance to CSF outflow was calculated as the absolute increase in intracranial pressure (interpolated over vasogenic waves) divided by the infusion rate (1.5 ml/min in most cases). The index of autoregulation was assessed as a correlation coefficient (moving time window of 5 min) between slow waves (with periods of 20 s to 2 min) in mean blood flow velocity and cerebral perfusion pressure.

RESULTS

The mean intracranial pressure increased during the test, from 6 mm Hg (standard deviation, 6 mm Hg) to 20 mm Hg (standard deviation, 10 mm Hg) (P < 0.0001). The index of autoregulation was significantly correlated with the resistance to CSF outflow (r = -0.41, P < 0.03), indicating better autoregulation with greater resistance to CSF outflow.

CONCLUSION

Patients presenting with ventricular dilation may exhibit either decreased (atrophy) or increased (normal-pressure hydrocephalus) resistance to CSF outflow. Increased resistance is correlated with preserved autoregulation. Patients with low resistance, suggesting brain atrophy, more often have disturbed autoregulation in the middle cerebral artery territory, as assessed by transcranial Doppler ultrasonography.

Responses of human frontal cortex to surprising events are predicted by formal associative learning theory

Learning depends on surprise and is not engendered by predictable occurrences. In this functional magnetic resonance imaging (fMRI) study of causal associative learning, we show that dorsolateral prefrontal cortex (DLPFC) is associated specifically with the adjustment of inferential learning on the basis of unpredictability. At the outset, when all associations were unpredictable, DLPFC activation was maximal. This response attenuated with learning but, subsequently, activation here was evoked by surprise violations of the learned association. Furthermore, the magnitude of DLPFC response to a surprise event was sensitive to the relationship that had been learned and was predictive of subsequent behavioral change. In short, the physiological response properties of right DLPFC satisfied specific predictions made by associative learning theory.

Age dependence of cerebrospinal pressure-volume compensation in patients with hydrocephalus

OBJECT

The dynamics of both drainage and storage capacity become altered during the sequential pathological processes that lead to hydrocephalus. Cerebrospinal fluid (CSF) formation and drainage rate have been reported to be age dependent. The aim of this study was to investigate whether CSF compensatory parameters are dependent on age in patients who have symptoms of hydrocephalus and apparently normal intracranial pressure (ICP).

METHODS

Forty-six patients who presented with ventriculomegaly, the clinical symptoms of hydrocephalus, and normal ICPs underwent a computerized CSF infusion test. Parameters used to describe CSF compensation were calculated and correlated with the age of each patient. The mean ICPs were found to be independent of the age of the patient. Resistance to CSF outflow (Rcsf), however, demonstrated a nonlinear increase with advancing age (r = -0.57; p < 0.0001) and was associated with a decrease in the CSF production rate, which also occurred with increasing age (r = 0.49; p < 0.002). Both the pulse amplitude of the ICP waveform and the slope of the amplitude-ICP regression line increased significantly with advancing age (r = 0.39; p < 0.01 and r = 0.43, p < 0.004, respectively). The nonlinear increase in the elastance coefficient indicated increasing brain stiffness, which acompanies older ages (r = -0.31; p < 0.04).

CONCLUSIONS

In a study of patients with symptoms of hydrocephalus, but normal ICPs, the increase in Rcsf and decrease in CSF production were most pronounced in patients who were older than 56 years of age. This relationship was more significant than previously suggested.

Guidelines for the microbiological quality of some ready-to-eat foods sampled at the point of sale. PHLS Advisory Committee for Food and Dairy Products

These guidelines for the microbiological quality of ready-to-eat foods represent a revision and expansion of guidelines first published by the PHLS in September 1992 and revised in March 1996. The latest guidelines incorporate many of the constructive comments received from food examiners and other microbiologists within and outside the PHLS and from environmental health officers throughout the United Kingdom. This document reviews the changes and the reasons they were made and sets out the new guidelines. It also clarifies the role of food examiners in interpreting the microbiological results of formal samples.

Population pharmacokinetics of enterally administered cisapride in young infants with gastro-oesophageal reflux disease

AIMS

To investigate the pharmacokinetics of enterally administered cisapride suspension in young infants being treated for gastro-oesophageal reflux disease.

METHODS

Plasma cisapride concentrations in 49 subjects (weight: 825-5010 g; n=108 samples, median two per patient; concentration: 14.8-170 ng ml-1 ) were fitted to a one-compartment model with first-order absorption and elimination in the NONMEM program using a logarithmic transformation of the observed and predicted concentrations. Fitting was achieved using the first order conditional estimation (FOCE) method with interaction between the interpatient and intrapatient variabilities. The interpatient variance of clearance (CL/F ) and volume of distribution (V /F ) and their covariance were estimated using an exponential error model. Intrapatient (residual) variance was estimated using an additive model.

RESULTS

The clearance of cisapride was shown to be linearly related to current body weight, slope: 0.538. The typical population values of CL/F, V /F and Ka (absorption rate constant) were 0.538 l h-1 kg-1, 21.9 l, and 2.58 h-1, respectively. The population coefficients of variation (CV%) for CL/F and V/F were 34.4% and 84.3%, respectively. The squared coefficient of correlation between random effects for CL/F and V /F was 0.45. The intrapatient variance was 0.15. V /F and Ka were not influenced significantly by any patient characteristic.

CONCLUSIONS

Cisapride pharmacokinetics in infants with reflux disease were satisfactorily described by a one-compartment model. Current weight should be taken into account when calculating maintenance cisapride doses in these infants.

Use of provisional restorations to enhance soft-tissue contours for implant restorations

The objective of restoring missing teeth with implant-supported restorations should not merely be achieving osseointegration with an implant and a biomechanically sound restoration. The objective must be the esthetic and functional restoration of the missing teeth. To achieve this, proper treatment planning is critical. Precise implant placement and delicate soft-tissue manipulation during surgery will allow the restorative dentist to enhance the peri-implant soft-tissue contours with the use of provisional restorations. Empirically, it seems that the earlier the provisional restoration is delivered in the treatment process the more ideal the esthetics. Several methods of using provisional restorations to enhance soft-tissue contours are presented. The concept of immediately delivering provisional restorations on placement of an implant is discussed.

The diagnosis of lameness associated with distal limb pathology in a horse: a comparison of radiography, computed tomography and magnetic resonance imaging

A cadaver limb from an eight-year-old horse with right forelimb lameness that was relieved with an intra-articular distal interphalangeal joint block was imaged with radiographs, spiral computed tomography (CT) and magnetic resonance imaging (MRI). Spiral CT demonstrated several lucencies within the deep digital flexor tendon immediately proximal to the navicular bone. On MRI these areas had increased signal and there was enlargement of the tendon at this site. Effusion in the proximal interphalangeal joint and navicular bursa and thinning of the fibrocartilage of the navicular bone were also observed on MRI images. These changes were not detected on radiographs. Histopathology confirmed that there were focal areas of collagen necrosis within the deep digital flexor tendon with thinning and degenerative changes in the fibrocartilage of the navicular bone.

Subtypes of Campylobacter jejuni from sporadic cases of diarrhoeal disease at different locations in England are highly diverse

Serotyping (heat stable antigens) was performed on 398 strains of Campylobacter jejuni from faeces of human enteritis cases in England. Strains isolated over 12 months at three locations were heterogeneous with 33 HS serotypes represented. HS1 and HS4 complex were the predominant types (34% of all strains). The monthly strain frequency distributions were similar at the three locations. The late spring peak appeared to be associated with a rise in miscellaneous serotypes rather than with the emergence of any characteristic predominant serotype. PFGE DNA restriction profiling provided evidence of a high degree of genomic diversity within the common HS1 and HS4 complex serotypes, irrespective of the geographical source, yet some subtypes were common to more than one location. The study showed that C. jejuni strain subtypes from human enteric infections in England were highly diverse, and that HS serotyping must be combined with a more discriminatory subtyping method such as PFGE DNA profiling to provide an accurate basis for epidemiological surveillance.

Enterotoxigenic Clostridium perfringens as a cause of sporadic cases of diarrhoea

The purpose of this study was to investigate the incidence of cases of sporadic diarrhoea associated with enterotoxigenic Clostridium perfringens. Cases were identified by detection of C. perfringens enterotoxin with the Oxoid RPLA kit, with confirmation by ELISA, in faecal specimens from isolated incidents of diarrhoea and from which no other enteropathogen had been isolated. In a 2-month study, 65 (18%) of 370 specimens were enterotoxin positive. There was no predominant age group or sex in the enterotoxin-positive group, but higher proportion (79%) was resident in the community than were enterotoxin-negative cases (34%). Only four of the 65 enterotoxin-positive patients had received antibiotic therapy. Spore counts in most enterotoxin-positive patients were < 10(5)/g, indicating that detection of high numbers of C. perfringens is not useful in determining the aetiology of sporadic diarrhoea. Diagnosis should be confirmed by the detection of enterotoxin, but further work is required to assess whether an acceptable accuracy is obtained with the RPLA kit or whether ELISA is needed in all cases.

Outpatient benzodiazepine detoxification procedure for methadone patients

Benzodiazepines are used by a substantial minority of opioid addicts on methadone maintenance. Alprazolam, now the most widely prescribed benzodiazepine in the United States, appears to have supplanted diazepam as the benzodiazepine drug of choice in this population. Its greater addiction liability, shorter half-life, and more intense withdrawal symptoms make addiction to alprazolam more likely and its management in methadone patients more complicated. This article describes a slow outpatient tapered reduction procedure that was utilized to detoxify benzodiazepine dependent methadone patients seen over a two-year period. The reduction procedure was offered to 22 opioid addicts on methadone maintenance who were regularly ingesting low to moderate amounts of benzodiazepines, primarily alprazolam. Of the 22 patients, 4 patients refused outpatient detoxification, and 18 were started on a reduction procedure. Twelve patients completed the detoxification procedure which averaged 7.8 weeks. Comparisons are made between completers and non-completers and essential design features of the procedure are discussed.

Microcephalic, osteodysplastic, primordial dwarfism

A case of microcephalic, osteodysplastic, primordial dwarfism (cephaloskeletal dysplasia of Taybi and Linder) is reported. This rare disease is characterised by unique clinical appearances and diagnostic radiographic findings. It is also associated with distinctive brain abnormalities. The latter include micrencephaly, lissencephaly, corpus callosum aplasia/agenesis and unusual histological brain abnormalities.

Pharmacokinetics of dexamethasone following single-dose intravenous administration to extremely low birth weight infants

The single-dose pharmacokinetics of dexamethasone were studied in 7 extremely low birth weight infants of mean (+/- SD) gestational age 25.6 +/- 0.5 weeks suffering bronchopulmonary dysplasia. A mean peak dexamethasone concentration of 250.5 +/- 70.7 ng/ml was obtained following an intravenous bolus dose (0.369 +/- 0.04 mg/kg dexamethasone) of dexamethasone sodium phosphate. Dexamethasone was measured in plasma by HPLC. Mean clearance (0.143 +/- 0.028 litres/kg/h) was approximately half that reported previously in children and adults, while the half-life (9.26 +/- 3.34 h) was 2- to 3-fold longer than in these patients. The volume of distribution (1.9 +/- 0.483 litres/kg) was larger than reported in a previous study in adults, but was similar to that determined in pediatric and adult patients in another study.

Characterization of the dissociation behavior of gas-phase protonated and methylated lactones

The dissociation behavior of gas-phase protonated and methylated four-, five-, six-, and seven-membered ring lactones, some with methyl substituents in various positions, has been characterized by using a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. The energy dependence of collisionally activated dissociation pathways was determined by energy-resolved mass spectrometry, and the dissociation behavior of the various protonated lactones was compared to that observed for protonated cyclic ketones and ethers of analogous ring size. The protonated cyclic ethers and ketones predominantly dissociated via dehydration, whereas the protonated lactones dissociated via losses of an alkene, ketene, and water. The dissociation behavior of the gas-phase methylated lactones formed from ion/molecule reactions with dimethyl ether ions was compared to the collisionally activated dissociation behavior of isomeric protonated methyl-substituted lactones. The methylation experiments indicated that the gas-phase addition of a methyl group may dramatically alter the favored dissociation pathways when compared to the simple protonated ions.

Methylene substitution reactions in a quadrupole ion trap selectivity of ethylene, ethylene oxide, and dimethyl ether reactive ions

To elucidate the selectivity of methylene substitution reactions of monosubstituted and disubstituted oxyaromatic compounds in a low pressure quadrupole ion trap environment, the relative abundances of covalently bound and loosely bound adducts formed by ion/molecule reactions with ethylene (ET), ethylene oxide (ETOX), and dimethyl ether (DME) were compared. Adduct ions of all three reagent gases were formed in both a conventional ion source and a quadrupole ion trap and characterized by collisionally activated dissociation. For DME and ET, the covalently bound adducts formed at (M + 45)(+) and (M + 41)(+), respectively, are direct precursors to the methylene substitution product ions at (M + 13)(+). ETOX and ET do not demonstrate the same functional group selectivity for methylene substitution as previously observed for DME. This is attributed to differences in reaction exothermicities and competing reactions.

[In vitro study of the microleakage pattern around posterior composite resin restorations using a new dentin bonding agent]

A totally new product, by the name Scotchbond 2 (3M Co) appeared recently in the field of bonding agents. Grace to its improved formula, the manufacturers claim that both the bond strength and the sealing ability of the material, render it trustful for use in both anterior and posterior composite resin restorations. The purpose of this in vitro investigation was to determine the microleakage pattern around slot type cavities, restored with posterior composite resin (P-50, 3M Co) using two different generations of bonding agents. Two types of cavities were prepared in sound premolars extracted for orthodontic reasons. In the first group (10 teeth) the cervical wall was located in the enamel, above the cementoenamel junction and in the second group (10 teeth) the cervical wall was located below the CEJ. The enamel surrounding the cavity margins was etched using 37% orthophosphoric acid gel, rinsed and dried and the bonding agents were applied and cured according to the manufacturer s instructions. The posterior composite was condensed and light-cured incrementally, in three horizontal layers. The samples were thermocycled for 200 cycles of 4 minutes each between 4.37 and 60 degrees centigrade, covered with fingernail varnish and sticky wax and immersed in 0.5% basic fuchsin dye for 12 hours. The specimens were split in two halves longitudinally in a mesiodistal direction in a hard tissues microtome and the degree of dye penetration was evaluated using an optical microscope. According to the results obtained we come to the conclusions that: 1. The use of Scotchbond 2 minimized but did not eliminate the microleakage around posterior composite resin restorations, in both types of cavities.(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary investigation of a disinfected gypsum die stone

The setting time, comprehensive strength, diametral tensile strength, expansion, and fine detail reproduction of disinfectant-containing die stones (Steri-Die A and Steri-Die B) were compared to two commonly used die materials (Vel-Mix and Die-Keen). Six samples of each die material were formed from polysulfide rubber, condensation silicone, polyether, and poly(vinyl siloxane) impression materials. The disinfected die stones compared favorably to the controls in all tests with the following exceptions: Steri-Die B was weaker in both compressive and tensile strength and deficient in detail reproduction, especially with condensation polymerizing silicone.

Esthetic results with full restorations

The metal-ceramic and all-ceramic esthetic restorations available today bear little resemblance to their predecessors of 2 and 3 decades ago. Metal-ceramic crowns and fixed partial dentures are successful when the dentist understands what biologic and mechanical demands will be placed on the restoration. Tissue management and tooth preparation affect long-term function and esthetic success.

Effect of electrodeposition of gold on porcelain-to-metal bond strength

The effect of electrodeposition of two different thicknesses of gold on porcelain-metal bond strength with three different base metal alloys was determined and compared to a control high gold alloy. The following conclusions can be drawn. Mean porcelain-metal bond strengths of all four alloys were in the same range when conventional porcelain application techniques were used. However, the base metal porcelain-metal bond is clinically suspect because of adhesive failure through the porcelain-metal interface. A thin 180A gold coat increased the porcelain-metal bond strength and generally resulted in cohesive failure through the porcelain. A thicker gold coat (720A) decreased the bond strength and generally resulted in adhesive failure. The mechanism of action of the gold coat on bond strength is likely its effect on the oxide layer on the surface of the base metal alloy.

Effect of four pretreatment techniques on porcelain-to-metal bond strength

Porcelain bond strengths of three base metal alloys with different metal pretreatment techniques were studied. Statistically significant differences were found in bond strengths achieved between the different metals but not with the different pretreatments. Each metal displayed considerable variation in bond strength with each of the pretreatment techniques. Collectively, the base metal alloys evaluated displayed a disturbing tendency for adhesive failure through the porcelain-metal interface, although this was not universal. Manufacturers and ceramists should develop a specific regime for porcelain bonding for each alloy used. Standardized testing should demonstrate adequate bond strengths with cohesive failure through the body of the porcelains.

[Follow-up (4.6 years) of patients with latent cardiomyopathy]

25 patients with latent cardiomyopathy (LCM) (filling pressure elevated during exercise) were followed. After 4.6 years 15 patients were re-examined (10 female, 5 male, mean age at first examination 47 years). 6 patients could not be reexamined, but it is certain that all 6 patients lived. 3 patients of whom 2 were foreigners could not be followed. 9 of these 15 re-examined patients showed 4.6 years after the first examination a normalization of filling pressures during exercise. Findings remained constant in 4 and became worse in 2 patients. There was a tendency for arterial blood pressure to increase during the 4.6 years. This small group of retrospectively followed patients with latent cardiomyopathy showed a favourable long-term result. The findings do not support the hypothesis that LCM is an early manifestation of dilated congestive cardiomyopathy.

An analysis of margin configurations for metal-ceramic crowns

Major types of margin configurations for ceramometal crowns are reviewed. This is one of the most commonly misunderstood and poorly practiced aspects of fixed prosthodontics. The resultant underprepared teeth produce discolored gingiva and chalky crowns.

Use of paint-on die spacers in preparations with grooves

Film thickness of paint-on die spacer materials was measured on axial walls and in grooves. Two different materials and two different modes of application were tested. From the data presented, the following conclusions can be drawn: There are potentially significant differences in film thickness produced with different die spacing materials. The technique used to apply die spacer can affect the film thickness produced. Careful application of Pactra airplane dope will not result in significant accumulation of die spacer in the groove. Tru-fit die spacer produced generally erratic film thickness and demonstrated a potentially significant amount of pooling in the groove base. Further study is warranted to determine if use of die spacer in grooves will improve the seating of castings.

Exposing the gingival margin: a systematic approach for the control of hemorrhage

Consistent and successful gingival deflection can be performed by controlling hemorrhage first. A systematic approach with contemporary materials has been described for various clinical situations to aid the dentist in the selection of an appropriate technique when gingival deflection is performed.

The esthetic metal-ceramic margin: a comparison of techniques

Metal-ceramic crowns with all-porcelain labial margins may have esthetic and biologic advantages. Several techniques for making these restorations have been described in the prosthodontic literature. The authors used all the techniques and compared the results in terms of quality and degree of difficulty in construction. Clinically acceptable results can be achieved with all described techniques. The advantages and disadvantages of each method are summarized in Table I.