A complicated Chiari type 1 malformation and holocord syrinx as a likely cause for heel pain

BACKGROUND

Chiari malformations are a rare group of rhomboencephalic abnormalities involving the brain, craniocervical junction and spine. They may manifest in a variety of clinical presentations which relate to the variable involvement of the cerebellum, brainstem, lower cranial nerves, spinal cord and altered CSF flow dynamics.

METHOD

We report an unusual case of incidental diagnosis of a type I Chiari malformation with secondary cystic cerebellar tonsillar encephalomalacia and holocord syrinx following investigation of a 5YO girl presenting with heel swelling related to progressive neuropathic osteoarthropathy of the posterior calcaneal body and apophysis.

RESULT

The child was treated with decompressive suboccipital craniectomy and C1 laminectomy and tonsillar resection. Cerebellar tonsillar gliosis and cystic degeneration were confirmed on histopathology. Referral for ongoing engagement with occupational and physical therapy.

CONCLUSION

Most type I Chiari malformations in the paediatric population are incidental and asymptomatic. Neurological symptoms are typically mild and relate to altered CSF flow dynamics; however, we present a complex case of type I Chiari malformation with an unusual constellation of associated complications.

Traumatic pseudoaneurysm of the internal iliac artery following bone marrow aspiration in a child: An extremely rare complication of a very common procedure

Presented here is a very rare and potentially life-threatening complication of a very common procedure. Vascular injury with traumatic pseudoaneurysm following BMAT in a paediatric patient has only been reported once in the literature to the best of our knowledge. Presented here is a second case, with pathognomonic imaging findings on CT that underwent successful coil embolisation.

Diffuse paediatric cerebellar glioma: two identical imaging phenotypes of an extremely rare entity with disparate pathology

Although the posterior fossa is a common location for paediatric brain tumours [1], diffuse glioma isolated to the cerebellum is an extremely rare imaging entity. Only two cases of isolated diffuse paediatric cerebellar glioma have been reported in the English language to the best of our knowledge [2, 3], and only one of these cases had a similar imaging phenotype to our cases [3]. Although somewhat similar to Lhermitte-Duclos (dysplastic gangliocytoma of the cerebellum), the appearances are distinct from other neoplastic entities of the paediatric posterior fossa. Clinical presentation and neurological examination findings are vital however to help differentiate other diffuse pathologies involving the cerebellum such as rhombencephalitis. Presented here are two diffuse cerebellar gliomas in children under the age of 3 with near identical imaging phenotypes demonstrating differing histological and molecular genetic profiles.

Previously unreported variant collateral supply in an acute stroke patient with anomalous common and internal carotid artery anatomy undergoing mechanical thrombectomy

Agenesis of the common carotid and internal carotid arteries are rare entities. Approximately 100 cases of internal carotid artery (ICA) agenesis are reported in the literature, and even fewer cases of common carotid agenesis. The collateral supply in such cases is well described and typically follows one of only a small number of variations. Lie classically described six major pathways of collateral supply in ICA agenesis (Congenital Anomalies of the Carotid Arteries. Excerpta Medica, Amsterdam, 1968; 35). Vasovic et al. in a comprehensive review of all published cases of common carotid agenesis have similarly described the typical variations in collateral supply seen in this setting. Neither described the anatomy presented here.

Does Medicare-eligible high-risk breast cancer screening MRI target the right women?

INTRODUCTION

MRI is the most sensitive modality to screen for breast cancer, but it is expensive with somewhat limited access. Audit of screening performance should reflect appropriate population targeting.

METHODS

An observational study on consecutively screened high-risk women, assessment of the contralateral breast staging a new cancer, or surveillance in women with prior breast cancer or high-risk lesion in Perth, Western Australia. All breast MRI studies from 1 January 2015 to 7 September 2018 were included. Studies were 3T comprising T2, DWI, ADC and T1-weighted +/- fat saturation +/- IV gadolinium, +/- subtraction. DCE was read on the dynamics or DynaCAD (Invivo, Gainesville, FL, USA). Fellowship-trained breast radiologists blindly double-read by consensus; additional reader/s arbitrated. The reference standard was the histopathology result or cancer registry notification for cancer diagnoses and benign biopsies, benign follow-up imaging or subsequent screening MRI.

RESULTS

Of 993 MRI studies in 554 women, 870 eligible MRI were performed in 471 women, and 706 had a reference standard. Median age was 44 years (range 18-80). The majority of studies (65% 457/706) were screening Medicare rebate-eligible high familial risk; 26% for surveillance after a breast cancer or contralateral staging; 6% screened BRCA carriers. Eleven cancers were diagnosed, eight were MRI-detected. Only two of these were at high-risk screening MRI. Five were detected at staging contralateral ILC, after negative 2D mammography and ultrasound. Cancer prevalence was highest for staging contralateral ILC, at 600/10,000 MRI, for high-risk screening 77/10,000 MRI and surveillance 116/10,000 MRI.

CONCLUSIONS

Cancers were predominantly detected in women undergoing preoperative staging of new invasive lobular carcinoma in the contralateral breast, rather than the Medicare rebate-eligible high-risk screening group.

A local case of fulminant primary amoebic meningoencephalitis due to Naegleria fowleri

Primary amoebic meningoencephalitis is an extremely rare, predominantly fulminant central nervous system infection caused by the amoeba Naegleria fowleri, first described in Australia in 1965. Despite the ubiquitous presence of N. fowleri, as few as 300 cases of infection have since been reported worldwide, with a case fatality rate approaching 98%. A combination of low index of suspicion, non-specific clinical findings and largely ineffective treatment modalities make this rapidly progressive meningoencephalitis virtually impossible to treat. Early and aggressive treatment utilising intravenous and intrathecal routes by a multidisciplinary team of neurosurgeons, intensivists and microbiologists is required. Presented is a case of a 56-year-old man who presented to the Gold Coast University Hospital in Queensland, Australia, with rapidly progressive primary amoebic meningoencephalitis. He received maximal therapy and died of his disease while in hospital.

RePHILL: protocol for a randomised controlled trial of pre-hospital blood product resuscitation for trauma

OBJECTIVES

To describe the 'Resuscitation with Pre-HospItaL bLood products' trial (RePHILL) - a multi-centre randomised controlled trial of pre-hospital blood product (PHBP) administration vs standard care for traumatic haemorrhage.

BACKGROUND

PHBP are increasingly used for pre-hospital trauma resuscitation despite a lack of robust evidence demonstrating superiority over crystalloids. Provision of PHBP carries additional logistical and regulatory implications, and requires a sustainable supply of universal blood components.

METHODS

RePHILL is a multi-centre, two-arm, parallel group, open-label, phase III randomised controlled trial currently underway in the UK. Patients attended by a pre-hospital emergency medical team, with traumatic injury and hypotension (systolic blood pressure <90 mmHg or absent radial pulse) believed to be due to traumatic haemorrhage are eligible. Exclusion criteria include age <16 years, blood product receipt on scene prior to randomisation, Advanced Medical Directive forbidding blood product administration, pregnancy, isolated head injury and prisoners. A total of 490 patients will be recruited in a 1 : 1 ratio to receive either the intervention (up to two units of red blood cells and two units of lyophilised plasma) or the control (up to four boluses of 250 mL 0.9% saline). The primary outcome measure is a composite of failure to achieve lactate clearance of ≥20%/h over the first 2 hours after randomisation and all-cause mortality between recruitment and discharge from the primary receiving facility to non-acute care. Secondary outcomes include pre-hospital time, coagulation indices, in-hospital transfusion requirements and morbidity.

RESULTS

Pilot study recruitment began in December 2016. Approval to proceed to the main trial was received in June 2017. Recruitment is expected to continue until 2020.

CONCLUSIONS

RePHILL will provide high-quality evidence regarding the efficacy and safety of PHBP resuscitation for trauma.

Three-year experience with interventional neuroradiology for management of cerebral aneurysms at a single Australian centre

INTRODUCTION

Over the last decade interventional neuroradiology (NR) has become the mainstay of managing cerebral aneurysms. The aim of our study was to review our growing experiences with interventional NR and quantify morbidity and mortality associated with these procedures.

METHODS

The electronic medical records of all patients admitted to the Gold Coast (University) Hospital Intensive Care Unit following subarachnoid haemorrhage (SAH) or elective interventional NR management of cerebral aneurysms between January 2012 and December 2014 were retrieved. Primary outcomes of interest were death, thromboembolic and haemorrhagic events during hospital admission.

RESULTS

One hundred and fifty-two patients underwent interventional NR procedures for cerebral aneurysms. This consisted of 92 (60.5%) elective cases and 60 (39.5%) emergency cases following SAH. The all-cause mortality rate and the rate of thromboembolic and haemorrhagic events for the entire cohort were 5.9%, 11.2% and 7.2% respectively. Intra-procedural complications occurred in 6.6% of the entire cohort. Median length of follow-up was 448 days, with 91.6% of the entire cohort followed up. At follow-up, 64.1% of patients had no neurological deficits, 29% had mild non-specific deficits and 6.9% had significant disability.

CONCLUSIONS

Interventional NR represents the primary treatment modality for all patients presenting to our service with cerebral aneurysm. Our results are encouraging and are comparable to published data in the international literature. Reducing the burden of thromboembolism in patients undergoing endovascular treatment of their aneurysmal disease is our main research focus currently, and we aim to improve outcomes for this patient group.

Obstetric skills drills: evaluation of teaching methods

OBJECTIVE

To determine the most effective method of delivering training to staff on the management of an obstetric emergency.

SUBJECTS

The research was conducted in a District General Hospital in the UK, delivering approximately 3500 women per year. Thirty-six staff, comprising of junior and senior medical and midwifery staff were included as research subjects. Each of the staff members were put into one of six multi-professional teams. Effectively, this gave six teams, each comprising of six members.

METHOD

Three teaching methods were employed. Lecture based teaching (LBT), simulation based teaching (SBT) or a combination of these two (LAS). Each team of staff were randomly allocated to undertake a full day of training in the management of Post Partum Haemorrhage utilising one of these three teaching methods. Team knowledge and performance were assessed pre-training, post training and at three months later. In addition to this assessment of knowledge and performance, qualitative semi-structured interviews were carried out with 50% of the original cohort one year after the training, to explore anxiety, confidence, communication, knowledge retention, enjoyment and transferable skills.

RESULTS

All teams improved in their performance and knowledge. The teams taught using simulation only (SBT) were the only group to demonstrate sustained improvement in clinical management of the case, confidence, communication skills and knowledge. However, the study did not have enough power to reach statistical significance. The SBT group reported transferable skills and less anxiety in subsequent emergencies. SBT and LAS reported improved multidisciplinary communication. Although tiring, the SBT was enjoyed the most.

CONCLUSION

Obstetrics is a high risk speciality, in which emergencies are to some extent, inevitable. Training staff to manage these emergencies is a fundamental principal of risk management. Traditional risk management strategies based on incident reporting and event analysis are reactive and not always effective. Simulation based training is an appropriate proactive approach to reducing errors and risk in obstetrics, improving teamwork and communication, whilst giving the student a multiplicity of transferable skills to improve their performance.

The immunomodulatory actions of E-type prostaglandins

Prostaglandins (PGs) have been recognised as modulators of immune responses. This has been proved by both in vitro studies and from observations in animals and humans. Administration of prostaglandins for therapeutic purposes, however, has been hampered by their limited bioavailability and their pleiotropic effects, with resultant toxicological profile. Despite this, some success has been demonstrated in the clinic for the control of graft rejection, especially when used as part of a broader immunosuppressant regimen. Full realisation of the therapeutic potential of prostaglandins will depend on a better understanding of their mechanism of action at the cellular level. Recently, it has been appreciated that prostaglandins do not merely inhibit T-cell function, but appear to modulate the profile of lymphocyte sub-populations through regulation of cytokine synthesis and release. Recent efforts have also begun to focus on identifying prostaglandin receptor subtypes important for immune regulation and offer a means, together with targeted delivery, of utilising the immunosuppressant/anti-inflammatory effects of E-type prostaglandins in a safe and effective manner.

New method to evaluate the practice of positive pressure ventilation in intensive care units

BACKGROUND

There is good evidence to support the use of a "protective" ventilation strategy, using small tidal volumes and inspiratory pressures, in patients with acute respiratory distress syndrome. Many general intensive care units in the UK are being slow to adopt this approach and we therefore set out to devise a method to audit ventilation and possibly influence practice in these units.

METHODS

Using variables that are routinely documented by intensive care nurses, we assessed the relationship between ventilator settings and arterial blood gas values on 30 consecutive ventilated patients admitted to intensive care units at both a teaching and a district hospital. Data were recorded twice daily and the proportions of data points where there was unnecessary hyperventilation were recorded at each centre.

RESULTS

The initial audit results showed clear differences in practice between the teaching hospital and the district hospital. After an intensive education programme, during which an active role for nursing staff in ventilator management was encouraged, supported by simple protocols, practice in the district hospital was re-audited and found to closely mirror that in the teaching centre.

CONCLUSIONS

To assist progress towards the use of a "protective" ventilation strategy in intensive care units in the UK, we devised a simple, robust audit method. We have shown how this method can give a more uniform practice of ventilation in critical care units, with the introduction of nurse-run protocols.

Direct optometrist referral of cataract patients into a pilot 'one-stop' cataract surgery facility

OBJECTIVES

To determine the feasibility of a) direct optometrist referral of patients with cataract, and b) combined assessment with same day cataract surgery ('one stop' cataract surgery).

METHODS

Evaluation of 169 patients referred directly by optometrists into a pilot 'one stop' cataract surgery facility.

RESULTS

Of 169 referrals, 160 patients (94.7%) were given confirmed appointments for the 'one stop' cataract service and 9 patients (5.3%) were appointed conventionally. Of 160 patients attending the 'one stop' cataract service, 154 patients (96.3%) underwent cataract surgery at the same visit, in 4 patients (2.5%) cataract surgery was indicated but deferred and in 2 patients (1.3%) cataract surgery was not indicated. The referral was supplemented with information regarding the patient's medical history forwarded by the general practitioner for 3 patients (1.8%). There were no systemic or sight-threatening complications. 151 patients (98.1%) achieved a visual acuity of 6/12 or better at a mean of 31 days post-operatively.

CONCLUSION

Optometrists can accurately predict the need for cataract surgery and refer directly into a pilot 'one stop' cataract surgery facility, without the need for general practitioner involvement. 'One stop' cataract surgery is feasible; benefits to the patient include the abolition of the need to visit the general practitioner for consultation and referral, and the hospital for pre-assessment.

Scintigraphic patterns of injury in amateur weight lifters

PURPOSE

Weight lifting is now a standard part of training in most sports. An increasing number of amateur athletes are doing strength training, mostly in unsupervised situations. A series of injuries in amateur weight lifters was analyzed by bone scintigraphy, with the aim of depicting specific patterns that would accurately identify the primary lesions.

METHODS

Twelve patients (10 men and 2 women) were studied whose ages ranged from 18 to 35 years. Patients were referred for bone scintigraphy with clinical diagnoses based on history, physical examination, and appropriate radiologic investigations. Diagnoses were confirmed by surgery, arthroscopy, arthrography, local steroid injection, and outcome.

RESULTS

Most of the injuries were in athletes undertaking free-weight training. Most injuries were in the upper limbs, particularly around the shoulder. Scintigraphic patterns of supraspinatus and bicipital tendons and also rotator cuff lesions were identified. Clavicular osteolysis, avulsion injuries, muscle damage, and vertebral lesions were also noted. Several abnormalities revealed by scintigraphy were clinically unsuspected.

CONCLUSIONS

Scintigraphic manifestations of several injuries, particularly around the shoulder, have a specific pattern. Recognition of these patterns can enhance the performance of bone scintigraphy. Scintigraphy also has the potential to detect clinically unsuspected disease.

Catheter patrols: a unique way to reduce the use of convenience urinary catheters

The increased risk of infections among elders has been was documented. Elder patients often have atypical signs and symptoms that lead to delays in diagnosis and treatment of infection. Urinary incontinence is often overlooked as a sign of infection because of the stereotypical belief that urinary incontinence is a normal part of the aging process. This belief can lead to overuse of indwelling urinary catheters and place the elder patient at even greater risk for infection. The Centers for Disease Control and Prevention's "Guidelines for Prevention of Catheter-Associated Urinary Tract Infections" lists four criteria that are helpful in determining appropriate urinary catheter usage. These guidelines, along with ongoing nursing assessment of the patient's urinary catheter need, play an important role in protecting elder patients from unnecessary catheter-associated urinary tract infections.

Noise levels in a cardiac surgical intensive care unit: a preliminary study conducted in secret

Noise in hospitals frequently exceeds recommended levels and has detrimental psychological and physiological effects on patients and staff. The aim of this study was to record the noise levels within the cardiac surgical intensive care unit (CSICU) environment in secret. The device used was a CEL Instruments environmental noise meter concealed in a dummy box featuring temperature and humidity digital displays. It allowed greater than 16 hours recording time at a 1-minute resolution. The 24-hour period was covered by overlapping recordings. The data collected were downloaded onto a personal computer for analysis. The maximum sound level recorded was 100.9 decibel level (dBA), 1 min Lmax (the maximum sound level occurring in a 1-min period). The minimum sound level was 61.3 dBA 1 min Lmax. The continuous background noise was at its lowest at 57.5 dBA 1 min equivalent continuous sound pressure levels (Leq) and at its peak 77.3 dBA 1 min Leq. Noise in the CSICU was above the recommended levels for patients and staff well-being. Future studies will be designed to establish a correlation between sound levels and events.

Cerebral magnetic resonance image segmentation using data fusion

OBJECTIVE

A semiautomated method is described for segmenting dual echo MR head scans into gray and white matter and CSF. The method is applied to brain scans of 80 healthy children and adolescents.

MATERIALS AND METHODS

A probabilistic data fusion equation was used to combine simultaneously acquired T2-weighted and proton density head scans for tissue segmentation. The fusion equation optimizes the probability of a voxel being a particular tissue type, given the corresponding probabilities from both images. The algorithm accounts for the intensity inhomogeneities present in the images by fusion of local regions of the images.

RESULTS

The method was validated using a phantom (agarose gel with iron oxide particles) and hand-segmented images. Gray and white matter volumes for subjects aged 20-30 years were close to those previously published. White matter and CSF volume increased and gray matter volume decreased significantly across ages 4-18 years. White matter, gray matter, and CSF volumes were larger for males than for females. Males and females showed similar change of gray and white matter volumes with age.

CONCLUSION

This simple, reliable, and valid method can be employed in clinical research for quantification of gray and white matter and CSF volumes in MR head scans. Increase in white matter volume may reflect ongoing axonal growth and myelination, and gray matter reductions may reflect synaptic pruning or cell death in the age span of 4-18 years.

A technique for single-channel MR brain tissue segmentation: application to a pediatric sample

A segmentation method is presented for gray matter, white matter, and cerebrospinal fluid (CSF) in thin-sliced single-channel brain magnetic resonance (MR) scans. The method is based on probabilistic modeling of intensity distributions and on a region growing technique. Interrater and intrarater reliabilities for the method were high, and comparison with phantom studies and hand-traced results from an experienced rater indicated good validity. The method was designed to account for spatially dependent image intensity inhomogeneities. Segmentation of MR brain scans of 105 (56 male and 49 female) healthy children and adolescents showed that although the total brain volume was stable over age 4-18, white matter increased and gray matter decreased significantly. There were no sex differences in total gray and white matter growth after correction for total brain volume. White matter volume increased the most in superior and posterior regions and laterality effects were seen in hemisphere tissue volumes. These findings are consistent with other reports, and further validate the segmentation technique.

An EP receptor with a novel pharmacological profile in the T-cell line Jurkat

1. Comparison of the rank order of potency of the natural prostanoids prostaglandin E2 (PGE2), PGD2, PGF2 alpha and carbaprostacyclin in stimulating cyclic AMP in Jurkat cells is consistent with the presence of an EP receptor. 2. Lack of responsiveness to the EP1/EP3 selective agonist, sulprostone, and the EP2 agonists, butaprost and AH 13205, indicates that this receptor is not of the EP1, EP2 or EP3 subtypes. 3. Inhibition of PGE2-stimulated cyclic AMP by the EP4 antagonist, AH 23848 is non-competitive, unlike the competitive antagonism reported in the pig saphenous vein EP4 preparation. Furthermore, 16,16-dimethyl PGE2 is 100 fold less potent than PGE2 in Jurkat cells, while these agonists are equipotent in the rabbit jugular vein purported EP4 preparation. In addition, 1-OH PGE1, which also is active in the rabbit jugular vein preparation, is inactive in Jurkat cells at concentrations up to 1 x 10(-4) M. These data are not wholly consistent with any adenylate cyclase coupled EP receptor described to date. 4. It is postulated that an EP receptor, positively coupled to adenylate cyclase, with a unique pharmacological profile is present in Jurkat cells.

The antiinflammatory activity of topically applied novel calcium-channel antagonists

The antiinflammatory activities of two novel calcium-channel antagonists, AGN 190742 and AGN 190744, were evaluated in murine models of cutaneous inflammation. These 2(5H)-furanone ring compounds block both depolarization-dependent Ca2+ entry and receptor-mediated responses in GH3 cells. Topical application of AGN 190742 or AGN 190744 inhibits neutrophil infiltration and epidermal hyperplasia induced by repeated treatment of mouse skin with phorbol ester. AGN 190744 also is active in an arachidonic acid model of acute inflammation. These data suggest that topical application of calcium-channel antagonists can inhibit cutaneous inflammatory responses and that AGN 190742 and/or AGN 190744 may serve as useful pharmacological probes for examining these responses in vivo.

Adsorption of cations to phosphatidylinositol 4,5-bisphosphate

We investigated the binding of physiologically and pharmacologically relevant ions to the phosphoinositides by making 31P NMR, electrophoretic mobility, surface potential, and calcium activity measurements. We studied the binding of protons to phosphatidylinositol 4,5-bisphosphate (PIP2) by measuring the effect of pH on the chemical shifts of the 31P NMR signals from the two monoester phosphate groups of PIP2. We studied the binding of potassium, calcium, magnesium, spermine, and gentamicin ions to the phosphoinositides by measuring the effect of these cations on the electrophoretic mobility of multilamellar vesicles formed from mixtures of phosphatidylcholine (PC) and either phosphatidylinositol, phosphatidylinositol 4-phosphate, or PIP2; the adsorption of these cations depends on the surface potential of the membrane and can be described qualitatively by combining the Gouy-Chapman theory with Langmuir adsorption isotherms. Monovalent anionic phospholipids, such as phosphatidylserine and phosphatidylinositol, produce a negative electrostatic potential at the cytoplasmic surface of plasma membranes of erythrocytes, platelets, and other cells. When the electrostatic potential at the surface of a PC/PIP2 bilayer membrane is -30 mV and the aqueous phase contains 0.1 M KCl at pH 7.0, PIP2 binds about one hydrogen and one potassium ion and has a net charge of about -3. Our mobility, surface potential, and electrode measurements suggest that a negligible fraction of the PIP2 molecules in a cell bind calcium ions, but a significant fraction may bind magnesium and spermine ions.

An in vivo phosphorus nuclear magnetic resonance study of the variations with age in the phosphodiester content of human muscle

Human gastrocnemius and slow twitch muscles contain phosphodiesters that may be detected in vivo by phosphorus nuclear magnetic resonance (NMR). This work represents a study of 354 spectra obtained from healthy subjects of various ages and from patients with peripheral vascular disease. The analysis of the data indicate a correlation between the concentration of phosphodiesters and age. By comparing the data obtained with healthy subjects and patients it is concluded that the increase in phosphodiesters is not due to disease, but to ageing itself. The significance of this increase is discussed.

Interaction of gentamicin and spermine with bilayer membranes containing negatively charged phospholipids

We measured the electrophoretic mobility of multilamellar phospholipid vesicles, the 31P NMR spectra of both sonicated and multilamellar vesicles, and the conductance of planar bilayer membranes to study the binding of spermine and gentamicin to membranes. Spermine and gentamicin do not bind significantly to the zwitterionic lipid phosphatidylcholine. We measured the concentrations of gentamicin and spermine that reverse the charge on vesicles formed from a mixture of phosphatidylcholine and either phosphatidylserine or phosphatidylinositol. From these measurements, we determined that the intrinsic association constants of the cations with these negative lipids are all about 10 M-1. This value is orders of magnitude lower than the apparent binding constants reported in the literature by other groups because the negative electrostatic surface potential of the membranes and the resultant accumulation of these cations in the aqueous diffuse double layer adjacent to the membranes have not been explicitly considered in previous studies. Our main conclusion is that the Gouy-Chapman-Stern theory of the aqueous diffuse double layer can describe surprisingly well the interaction of gentamicin and spermine with bilayer membranes formed in a 0.1 M NaCl solution if the negative phospholipids constitute less than 50% of the membrane. Thus, the theory should be useful for describing the interactions of these cations with the bilayer component of biological membranes, which typically contain less than 50% negative lipids. For example, our results support the suggestion of Sastrasinh et al. [Sastrasinh, M., Krauss, T. C., Weinberg, J. M., & Humes, H. D. (1982) J. Pharmacol. Exp. Ther. 222, 350-358] that phosphatidylinositol is the major binding site for gentamicin in renal brush border membranes.

Bilayer membranes containing the ganglioside GM1: models for electrostatic potentials adjacent to biological membranes

Although the Gouy-Chapman-Stern theory of the aqueous diffuse double layer describes well the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes, it does not describe adequately the zeta potential of biological membranes: the zeta potential of an erythrocyte is about half the value predicted from the theory by using the known density of negatively charged sialic acid residues. To investigate the factors responsible for this low electrophoretic mobility, we formed membranes from mixtures of the zwitterionic lipid phosphatidylcholine, PC, and the glycolipid galactosyl-N-acetylgalactosaminyl(N-acetylneuraminyl) -galactosylglucosylceramide, GM1. This glycolipid differs from phospholipids in two respects. First, the negative charge on GM1 is located about 1 nm from the surface, which tends to increase the electrophoretic mobility of vesicles. Second, the head group of GM1 contains five sugar groups that exert a hydrodynamic drag, which tends to decrease the mobility of the vesicles. In a decimolar monovalent salt solution, where the Debye length is about 1 nm, the electrophoretic mobility of the PC-GM1 vesicles is about half the mobility of PC-phosphatidylserine or PC-phosphatidylglycerol vesicles of equivalent composition. In addition, conductance measurements with planar bilayer membranes as well as 31P nuclear magnetic resonance and fluorescence measurements with sonicated vesicles indicate that the potential at the surface of PC-GM1 membranes is about half the value measured for PC-phosphatidylserine membranes in a 0.1 M monovalent salt solution.

A radionuclide method of evaluating shunt function and CSF circulation in hydrocephalus. Technical note

A simple technique for the evaluation of shunt function and cerebrospinal fluid (CSF) circulation in hydrocephalic patients is described. The method utilizes clearance rates of a radionuclide tracer injected into the lateral ventricle via an indwelling frontal catheter which is separate from the shunt apparatus. This permits an accurate assessment of drainage of ventricular CSF via the shunt, or the patency of normal or alternative CSF pathways where the shunt is malfunctioning.

Appearance of Ga-67 citrate scanning in a patient with Mikulicz's syndrome associated with non-Hodgkin's lymphoma. A case report

The case of a patient with Mikulicz's syndrome and associated non-Hodgkin's lymphoma is described. Description of the Ga-67 scan in Mikulicz's syndrome is presented.

Large divalent cations and electrostatic potentials adjacent to membranes. Experimental results with hexamethonium

A simple extension of the Gouy-Chapman theory predicts that the ability of a divalent cation to screen charges at a membrane-solution interface decreases significantly if the distance between the charges on the cation is comparable with the Debye length. We tested this prediction by investigating the effect of hexamethonium on the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes. The distance between the two charges of an extended hexamethonium molecule is approximately 1 nm, which is the Debye length in the 0.1 M monovalent salt solutions used in these experiments. Six different experimental approaches were utilized. We measured the electrophoretic mobility of multilamellar vesicles to determine the zeta potential, the line width of the 31P nuclear magnetic resonance (NMR) signal from sonicated vesicles to calculate the change in potential at the phosphodiester moiety of the lipid, and the conductance of planar bilayer membranes exposed to either carriers (nonactin) or pore formers (gramicidin) to estimate the change in potential within the membrane. We also measured directly the effect of hexamethonium on the potential above a monolayer formed from negative lipids, and attempted to calculate the change in the surface potential of a bilayer membrane from capacitance measurements. With the exception of the capacitance calculations, each of the techniques gave comparable results: hexamethonium exerts a smaller effect on the potential than that predicted by the classic screening theory. The results are consistent with the predictions of the extended Gouy-Chapman theory and are relevant to the interpretation of physiological and pharmacological experiments that utilize hexamethonium and other large divalent cations.

Dimethonium, a divalent cation that exerts only a screening effect on the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes

Calcium and other alkaline earth cations change the electrostatic potential adjacent to negatively charged bilayer membranes both by accumulating in the aqueous diffuse double layer adjacent to the membrane and by adsorbing to the phospholipids. The effects of these cations on the electrostatic potential are described adequately by the Gouy-Chapman-Stern theory. We report the results of experiments with ethane-bis-trimethylammonium, a cation that has been termed "dimethonium" or "ethamethonium" in analogy with hexamethonium (hexane-1,6-bis-trimethylammonium) and decamethonium (decane-1,10-bis-trimethylammonium). We examined the effect of dimethonium on the zeta potential of multilamellar vesicles formed from the negative lipid phosphatidylserine (PS) and from 5:1 phosphatidylcholine/phosphatidylserine mixtures in solutions containing 0.1, 0.01 and 0.001 M sodium, cesium, or tetramethylammonium chloride. We also examined the effect of dimethonium on the conductance of planar PS bilayer membranes and the 31P NMR signal from sonicated PS vesicles formed in 0.1 M NaCl. We found no evidence that dimethonium adsorbs specifically to bilayer membranes. All the results, except for those obtained with vesicles of low charge density formed in a solution with a high salt concentration, are consistent with the predictions of the Gouy-Chapman theory. We conclude that dimethonium, which does not have the pharmacological effects of hexamethonium and decamethonium, is a useful divalent cation for physiologists interested in investigating electrostatic potentials adjacent to biological membranes.

Comparison of thallium-201 scanning in idiopathic dilated cardiomyopathy and severe coronary artery disease

To determine whether cardiomyopathy could be distinguished from coronary artery disease, we used thallium scanning to study 25 patients with severe left ventricular dysfunction and chronic heart failure. Ten patients had normal coronary arteries and idiopathic cardiomyopathy (ejection fraction 20 +/- 5%), and 15 patients had multivessel coronary disease and left ventricular dysfunction (ejection fraction 25 +/- 6%). The exercise time and maximal heart rate were similar in the two groups. Two patients with cardiomyopathy and 11 with coronary artery disease had a positive exercise ECG (p less than 0.05). Thallium scans showed perfusion defects in all 25 patients. The perfusion defects were complete in nine coronary artery disease patients (60%) and in one patient (10%) with cardiomyopathy (p less than 0.05). Extensive defects involving more than 40% of the left ventricular circumference, the number of segments involved, redistribution on the 4-hour scan, lung uptake and ventricular size were similar in the two groups. Perfusion defects on thallium scanning can occur in patients with idiopathic dilated cardiomyopathy and chronic heart failure. Thallium scanning cannot be reliably used in patients with chronic heart failure to distinguish coronary artery disease from cardiomyopathy unless complete defects are present.

The adsorption of divalent cations to phosphatidylglycerol bilayer membranes

The ability of Stern equation to describe the adsorption of divalent cations to phosphatidylglycerol membranes was tested by combining 31P-NMR and electrophoretic mobility measurements. In 0.1 M sodium chloride both the 31P-NMR and the zeta potential data are well described by the Stern equation. 31P-NMR and 13C-NMR results indicate that cobalt forms inner-sphere complexes only with the phosphate group of phosphatidylglycerol molecules and that a substantial fraction of the adsorbed cobalt ions form outer-sphere complexes. Evidence is presented that suggests the alkaline earth cations also bind to phospholipids mainly by forming outer sphere complexes. Electrophoretic mobility measurements were performed with several different divalent cations. In all cases the zeta potentials in 0.1 M sodium chloride were well described by the Stern equation. The intrinsic 1:1 association constants (M-1) for the phosphatidylglycerol complexes decreased in the sequence: Mn2+, 11.5; Ca2+, 8.5; Ni2+, 7.5; Co2+, 6.5; Mg2+, 6.0; Ba2+, 5.5 and Sr2+, 5.0.

Exercise-induced ST-segment elevation in leads V1 or aVL. A predictor of anterior myocardial ischemia and left anterior descending coronary artery disease

Exercise-induced ST-segment elevation in leads V1 and/or aVL in the absence of anterior Q waves occurred in 46 of 190 patients (24%) who underwent 12-lead exercise electrocardiography with thallium-201 myocardial perfusion imaging and coronary arteriography. Significant left anterior descending coronary artery (LAD) disease was present in 38 of 46 patients (83%) with V1/aVL ST evaluation and in 72 of 144 patients (50%) without V1/aVL ST elevation (p less than 0.0005). Anterior myocardial ischemia, indicated by reversible anterior perfusion defects on thallium scanning, was present in 40 of 46 patients (87%) with V1/aVL ST elevation and in 25 of 144 patients (17%) without V1/aVL ST elevation (p less than 0.0005). Exercise ST elevation in V1/aVL was detected in 38 of 110 of the patients (35%) with LAD disease, for a specificity of 90%, and in 40 of 65 of the patients (62%) with anterior myocardial ischemia, for a specificity of 95%. We conclude that during 12-lead exercise electrocardiography, ST-segment elevation in V1 and/or a VL in the absence of anterior Q waves predicts anterior myocardial ischemia and LAD disease.

Adsorption of divalent cations to bilayer membranes containing phosphatidylserine

The Stern equation, a combination of the Langmuir adsorption isotherm, the Boltzmann relation, and the Grahame equation from the theory of the diffuse double layer, provides a simple theoretical framework for describing the adsorption of charged molecules to surfaces. The ability of this equation to describe the adsorption of divalent cations to membranes containing brain phosphatidylserine (PS) was tested in the following manner. Charge reversal measurements were first made to determine the intrinsic 1:1 association constants of the divalent cations with the anionic PS molecules: when the net charge of a PS vesicle is zero one-half of the available sites are occupied by divalent cations. The intrinsic association constant, therefore, is equal to the reciprocal of the divalent cation concentration at which the mobility of a PS vesicle reverses sign. The Stern equation with this association constant is capable of accurately describing both the zeta potential data obtained with PS vesicles at other concentrations of the divalent cations and the data obtained with with vesicles formed from mixtures of PS and zwitterionic phospholipids. Independent measurements of the number of ions adsorbed to sonicated PS vesicles were made with a calcium-sensitive electrode. The results agreed with the zeta potential results obtained with multilamellar vesicles. When membranes are formed at 20 degrees C in 0.1 M NaCl, the intrinsic 1:1 association constants of Ni, Co, Mn, Ba, Sr, Ca, and Mg with PS are 40, 28, 25, 20, 14, 12, and 8 M-1, respectively.

Serial exercise thallium myocardial perfusion scanning and exercise electrocardiography in the diagnosis of coronary artery disease

Serial exercise thallium-201 myocardial perfusion scanning (exercise and 4-hour redistribution) was compared to rest and exercise electrocardiography (ECG) for the detection of coronary artery disease in 125 patients with known or suspected coronary artery disease. All patients underwent coronary arteriography and 108 were found to have significant coronary artery lesions. The serial exercise thallium scan was significantly more sensitive than rest and exercise ECG in detecting coronary artery disease (94% v. 83% P less than 0.01). The sensitivity of a reversible thallium perfusion scan abnormality and a positive exercise ECG for detecting exercise induced myocardial ischaemia in coronary artery disease was similar (69% v. 63%). The exercise thallium scan complemented the exercise ECG, and the sensitivity of the combined test was significantly greater than the exercise ECG alone (84% v. 63% P less than 0.001). The specificity for coronary artery disease of the exercise ECG was 65% and that of the exercise thallium-201 myocardial perfusion scan was 82% (P = NS). Thallium-201 myocardial perfusion scanning complements the rest and exercise ECG in the non-invasive detection of coronary artery disease.

The adsorption of divalent cations to phosphatidylcholine bilayer membranes

Electrophoretic mobility and 31P NMR measurements were combined to test whether the combination of the Henry, Boltzmann and Grahame equations is capable of describing the adsorption of divalent cations of phosphatidylcholine membranes. Cobalt was chosen for this study because, of all the common divalent cations, its effects on the 31P NMR spectrum of phosphatidylcholine membranes are easiest to interpret. Both the 31P NMR data on the adsorption of cobalt and the zeta potential data calculated from the electrophoretic mobility in the presence of cobalt are well described by the combination of these three equations. Electrophoretic mobility measurements were also performed with a number of other divalent cations and the zeta potentials were, in all cases, well described by the combination of these three equations. The binding deduced from such measurements decreases in the sequence: Mn2+, Mg2+, Ca2+, Co2+, Ni2+, Sr2+, Ba2+. If we assume that a lipid molecule occupies an area of 60 A2 and that there is a 1 : 1 stoichiometry for the binding of the divalent ions to phosphatidylcholine, the dissociation constants are, respectively: 0.3, 1.0, 1.0, 1.2, 1.2, 2.8, 3.6 M.