494 DISCOMFORT IN PEOPLE WITH DEMENTIA ADMITTED TO AN ACUTE GENERAL MEDICAL HOSPITAL: A HOSPITAL CROSS SECTIONAL STUDY OF PREVALENCE

Introduction

The acute hospital is a challenging place for a person with dementia whose ability to communicate discomfort and need is impaired. Their discomfort may go unnoticed due to insufficient staffing and time resources in this acute environment. Concerns have been raised about the consequences of these overlooked discomfort (e.g. distress and agitation), and hence how we can correctly identify their sources and severity. This study aimed to describe the source of discomfort and challenging behaviours in people with dementia (PwD) in UK acute hospital.

Method

A cross-sectional observational study of 49 patients with dementia admitted to a NHS acute hospital. Their discomfort was detected and its sources were identified (Sources of Discomfort Scale) during an hour observation when they were at rest and moved by staff. Their challenging behaviours were also recorded (Neuropsychiatric Inventory) through interviewing with the ward staff, as well as documentation of severity of dementia and presence of delirium.

Results

The overall prevalence of discomfort was 98%, with excessively sleepy or tired being the commonest; 39 (80%) participants experienced three or more type of discomfort. The commonest sources of discomfort were physical (e.g. constipation) and environmental (e.g. physically restrained), affecting up to 43 (88%) and 42 (83%) participants respectively. There was also evidence of an association between delirium and sleepiness or tiredness’s discomfort, meaning that PwD with delirium were nearly triply as likely to feel uncomfortable because of sleepiness or tiredness. Challenging behaviours affected over 80% of our participants, with agitation or aggression being the commonest. On average, these behaviours were moderately severe.

Conclusion

Discomfort and challenging behaviours were very common in PwD admitted to acute hospitals. Patients and staff would benefit from more accurate and frequent detection of discomfort by focusing on non-pain-related discomfort and using observational scales.

540 Point of Care Testing for Tetanus Immunity: A Systematic Review

Introduction

All patients presenting to emergency departments (EDs) with traumatic injuries require tetanus immunity assessments. Inaccurate tetanus vaccination history based on patient recall incurs unnecessary costs on the NHS. Point-of-care immunochromatographic tests (Tetanus Quick Sticks [TQS]) quickly identify tetanus immunity status. We aim to evaluate the diagnostic accuracy and cost-efficacy of TQS to assess their relevance in emergency care.

Method

The systematic review followed PRISMA guidelines. A retrospective search of MEDLINE, Embase, Global Health, HMIC and The Cochrane Library was conducted. Studies were eligible if sensitivity, specificity, or cost-efficacy of TQS were reported. At least two authors independently analysed the data from each study.

Results

12 studies were suitable for inclusion (n = 1,662,865 participants): one retrospective and 11 prospective observational cohort studies. Eight studies assessed diagnostic accuracy with the median sensitivity at 86% (55-100) and the median specificity at 97.5% (1-100). All six studies investigating cost-efficacy reported greater savings when using TQS instead of using vaccination history, due to a decrease in unnecessary tetanus vaccine and immunoglobulin administration.

Conclusions

TQS is a safe diagnostic tool, especially when used by trained operators. TQS widely reduces costs in comparison to traditional vaccination history. We recommend the use of TQS in Emergency Departments throughout the NHS.

Bounds on the attractor dimension for magnetohydrodynamic channel flow with parallel magnetic field at low magnetic Reynolds number

We investigate aspects of low-magnetic-Reynolds-number flow between two parallel, perfectly insulating walls in the presence of an imposed magnetic field parallel to the bounding walls. We find a functional basis to describe the flow, well adapted to the problem of finding the attractor dimension and which is also used in subsequent direct numerical simulation of these flows. For given Reynolds and Hartmann numbers, we obtain an upper bound for the dimension of the attractor by means of known bounds on the nonlinear inertial term and this functional basis for the flow. Three distinct flow regimes emerge: a quasi-isotropic three-dimensional (3D) flow, a nonisotropic 3D flow, and a 2D flow. We find the transition curves between these regimes in the space parametrized by Hartmann number Ha and attractor dimension d(att). We find how the attractor dimension scales as a function of Reynolds and Hartmann numbers (Re and Ha) in each regime. We also investigate the thickness of the boundary layer along the bounding wall and find that in all regimes this scales as 1/Re, independently of the value of Ha, unlike Hartmann boundary layers found when the field is normal to the channel. The structure of the set of least dissipative modes is indeed quite different between these two cases but the properties of turbulence far from the walls (smallest scales and number of degrees of freedom) are found to be very similar.

Dermatological conditions in military conscripts

BACKGROUND

Published studies regarding skin conditions in the military are mainly cross-sectional studies from clinical encounters during war campaigns and military training.

AIMS

To determine the incidence and spectrum of dermatological conditions in a cohort of military conscripts in Singapore. Soldiers diagnosed with contact dermatitis (CD) were further analysed for body area involvement, possible occupational and/or environmental causative agent and restrictions issued.

METHODS

Retrospective cohort study. Subjects' diagnoses and demographic variables were extracted from electronic medical records. Medical records of CD cases were reviewed to characterize the nature of exposure and operational impact on training.

RESULTS

The incidence of reporting of new dermatological complaints was 24.5 per 100 military conscripts per year. Dermatological conditions with the highest incidence over the period of full-time military service included fungal skin infection (6.7/100 conscripts/year), non-specific dermatitis (4.9/100 conscripts/year) and insect bite reaction (1.8/100 conscripts/year). The annual incidence of contact dermatitis over the same period was 0.4/100 conscripts.

CONCLUSIONS

In a military population based in the tropics fungal skin infections, non-specific dermatitis and insect bite reactions were the commonest reasons for dermatological consultation. CD incidence was 0.4 per 100 conscripts per year.

Aviation Medicine: global historical perspectives and the development of Aviation Medicine alongside the growth of Singapore's aviation landscape

Aviation Medicine traces its roots to high altitude physiology more than 400 years ago. Since then, great strides have been made in this medical specialty, initially catalysed by the need to reduce pilot medical attrition during the World Wars, and more recently, fuelled by the explosive growth in globalised commercial air travel. This paper traces the historical milestones in Aviation Medicine, and maps its development in Singapore since the 1960s. Advancements in military aviation platforms and technology as well as the establishment of Singapore as an international aviation hub have propelled Aviation Medicine in Singapore to the forefront of many domains. These span Aviation Physiology training, selection medical standards, performance maximisation, as well as crew and passenger protection against communicable diseases arising from air travel. The year 2011 marks the centennial milestone of the first manned flight in Singapore, paving the way for further growth of Aviation Medicine as a mature specialty in Singapore.

Self-expanding nitinol stents in recanalisation of long-length superficial femoral artery occlusions in patients with critical limb ischaemia

INTRODUCTION

This study aims to evaluate our experience with self-expanding nitinol stent- enabled recanalisation of long-length occlusions (30 cm or more) of the superficial femoral artery (SFA).

METHODS

573 patients underwent 842 lower limb interventions from August 2006 to December 2008. A retrospective review of patients undergoing recanalisation of long-length SFA occlusions with self-expanding nitinol stents and an evaluation of their patency and impact on limb salvage, were done.

RESULTS

22 patients (mean age 62.5 years, male: female ratio 11:11) underwent 22 long-length SFA stenting procedures. The spectrum of critical limb ischaemia included rest pain (five), ulcer (six) and gangrene (11). Length of occlusions varied from 30 cm to 45 cm (average length 36.4 cm). Five patients had stents placed through the ipsilateral popliteal artery approach, and the rest had stents placed through the femoral artery approach. All patients were followed up over an average duration of 12 months. One patient died due to associated medical conditions during this period. Six out of 21 (28.6 percent) of the stents thrombosed completely on one year follow-up. Of these, two patients underwent amputation, one patient had a bypass, and the stent in two patients were recanalised with balloon angioplasty. All remaining patent stents showed varying degrees of stenoses at one year. The overall limb salvage rate at one year following stent placement was 81 percent.

CONCLUSION

Our experience showed the beneficial result of long-length SFA stent placement with good limb salvage outcome. Repeat interventions may be required to maintain the patency of stents in these patients.

Atypical hearing loss in women with breast cancer receiving adjuvant treatment

There are no reports of adjuvant treatments for early breast cancer causing hearing loss. Yet in this exploratory study 14/16 women who had received Fluorouracil, Epirubicin and Cyclophosphamide (FEC) chemotherapy regimen, 11 of whom also received endocrine treatment, had reduced hearing sensitivity, with 9/16 being atypical. It is not clear whether this finding is related to oestrogen reduction and/or ototoxicity but a more detailed investigation in this area is warranted given the large number of women with breast cancer who receive adjuvant treatments.

Comparison of PRE-dilatation vs direct stenting in coronary treatment using the Medtronic AVE S670 Coronary Stent System (the PREDICT trial)

Current stent delivery systems make primary stenting (stent placement without predilatation) possible, but few controlled trials have been performed to evaluate the success, safety, cost saving, and potential benefit of this approach in reducing late restenosis. The Comparison of PRE-Dilatation Versus Direct Stenting In Coronary Treatment using the Medtronic AVE S670 Coronary Stent System trial was a 399-patient study comparing results with the Medtronic-AVE S670 stent to objective performance criteria based on prior approved stents, with subrandomization to direct stenting versus stenting after balloon predilatation. Overall, results with the S670 stent showed excellent success and safety, with delivery success of 99%, a 14-day adverse event rate of 6.8% (including 6.5% non-Q-wave myocardial infarction), and favorable angiographic (20%) and clinical (12%) restenosis rates. Direct stenting was successful in 92% of cases, with a 99.5% secondary success rate including additional pretreatment of initially unsuccessful direct-stenting attempts, and no increase in complications. There were modest ( approximately 10%) savings in fluoroscopy time, contrast use, and a decrease in angioplasty balloon use (0.6 vs 1.3 balloons/case), but no reduction in clinical or angiographic restenosis. Patients treated later in the study, with a device that had less balloon extension beyond the edges of the stent, had slightly lower angiographic restenosis rates (19% vs 23%). In conclusion, the S670 stent showed excellent overall performance. Although direct stenting was safe and highly successful, it offered only modest cost savings, and no reduction in late restenosis compared with stenting after predilatation.

Defining and supporting the diverse information needs of community-based care using the web and hand-held devices

Community-based healthcare focused on maintaining wellness is becoming increasingly prevalent in the United States in an effort to eliminate healthcare disparities and reduce healthcare costs. These community-oriented initiatives, however, often require partnerships that cross traditional boundaries. As a result, these initiatives often lack a common information infrastructure to support the care delivery process. We have created and implemented a Web-based information and communication system to support the needs of a community-based healthcare project for Medicaid beneficiaries in Durham County, North Carolina. Through this project, we have identified the relevant information requirements and stakeholders for community-based care. In addition, we have explored the use of hand-held devices for accessing and collecting clinical information in the field. The overall goal of this project is to lower the costs and improve the quality of community-based healthcare through improved handling of information.

Microvessel precursor smooth muscle cells express head-inserted smooth muscle myosin heavy chain (SM-B) isoform in hyperoxic pulmonary hypertension

The present study analyzes smooth muscle myosin heavy chain (SMMHC) expression as lung microvascular precursor smooth muscle cells (PSMCs), cells derived from fibroblasts and intermediate cells (immature SMCs), acquire a smooth muscle phenotype in an in vivo model of pulmonary hypertension (PH). Because of the unique contractile properties of the SMMHC isoform SM-B, we analyzed its expression in the microvessels (<100 micrometers diameter) and in larger vessels (100-700 micrometers) quantitatualy by the labeled [strept]avidin-biotin technique (day 1-28), and related this to cell phenotype by transmission microscopy and protein A-gold labeling (at day 28). Airway SMCs of the normal and hypertensive lung uniformly expressed SM-B whereas vascular SMC expression was heterogeneous. Thus, in some large arteries (and veins) SMCs contained cells expressing SM-B while in others all the cells were immunonegative. Microvascular cells expressing SM-B (arteries and veins) were rare in normal lung and numerous in PH, increasing as wall muscle developed in smaller segments with time. As in large vessels, some microvessels had immunopositive cells and others only negative ones. Ultrastructural analysis confirmed that the SMCs of bronchial vessels, and the septal SMCs adjoining alveolar ducts, contained dense filament arrays decorated with SM-B. While the PSMC processes of the normal lung contained sparse filaments decorated with SM-B, these cells expressed dense filament arrays in PH. Fibroblasts migrating to align around the microvessels also expressed SM-B but in the absence of a filament network. For the first time, we demonstrate in vivo that newly developed microvascular PSMCs express the SMMHC SM-B isoform in PH.

Detection of reovirus RNA in hepatobiliary tissues from patients with extrahepatic biliary atresia and choledochal cysts

Extrahepatic biliary atresia (EHBA) and choledochal cysts (CDC) are important causes of obstructive jaundice in pediatric patients. Viruses in general, and reoviruses in particular, have long been considered as possible etiologic agents responsible for inciting the inflammatory process that leads to these infantile obstructive cholangiopathies. In an effort to determine whether reovirus infection is associated with these disorders, we used a sensitive and specific reverse-transcriptase polymerase chain reaction (RT-PCR) technique designed to amplify a portion of the reovirus L1 gene segment from extracts of liver and/or biliary tissues. These tissues were obtained at the time of liver biopsy or surgical procedures from 23 patients with EHBA, 9 patients with CDC, and 33 patients with other hepatobiliary diseases. Hepatic and biliary tissues obtained at autopsy from 17 patients who died without known liver or biliary disease were also analyzed. Reovirus RNA was detected in hepatic and/or biliary tissues from 55% of patients with EHBA and 78% of patients with CDC. Reovirus RNA was found also in extracts of hepatic and/or biliary tissue from 21% of patients with other hepatobiliary diseases and in 12% of autopsy cases. The prevalence of reovirus RNA in tissues from patients with EHBA and CDC was significantly greater than that in patients with other hepatobiliary diseases (chi2 P = .012 EHBA vs. OTHER, P = .001 CDC vs. OTHER), or AUTOPSY cases (chi2 P = .006 EHBA vs. AUTOPSY, P < .001 CDC vs. AUTOPSY).

Does Acanthamoeba protect Pseudomonas aeruginosa from the bactericidal effects of contact lens disinfecting systems?

PURPOSE

The aim of this study was to test the hypothesis that Pseudomonas aeruginosa that have been internalized in Acanthamoeba are protected against the action of contact lens disinfecting solutions.

METHODS

The experiments were divided into two parts. First, five commercially available disinfecting solutions, hydrogen peroxide and non-peroxide based, were tested for their efficacy against four strains of P. aeruginosa and one strain of A. castellanii. Cells were inoculated into working concentrations of disinfecting solutions, incubated for 18 h and the numbers of viable bacteria or amoeba were analysed after appropriate growth on agar plates. Second, two strains of P. aeruginosa were allowed to interact with A. castellanii for 4 h prior to addition to disinfecting solutions. The numbers of P. aeruginosa after incubation with the disinfecting solutions were measured after growth on agar plates.

RESULTS

In general, disinfecting solutions containing hydrogen peroxide were most effective against the micro-organisms. Solutions containing only traces of polyaminopropyl biguanide were least effective.

CONCLUSIONS

For strains of P. aeruginosa, the presence of the amoebae did not protect the bacteria against the disinfecting agents. The amoeba appeared to kill the bacteria, perhaps using them as a food source.

Down-regulation of plant V-type H+ -ATPase genes after light-induced inhibition of growth

Cell extension growth in the mesocotyl tip of dark-grown Zea mays L. seedlings is dependent on vacuole enlargement and massive flux of ER and Golgi vesicles. Water flow into the expanding vacuole is driven by ion accumulation, which in turn is energized by the vacuolar H+-ATPase (V-ATPase). The V-ATPase energizes the secondary ion transport into the expanding vacuole. As light exposure leads to a strong inhibition of extension growth, the effect of light on transcript levels for subunits A and c of the V-ATPase was analyzed. Partial homologous cDNAs for subunit A and two isoforms of subunit c were cloned by RT-PCR. In dark-grown seedlings transcript levels for both subunits were much higher in the growing mesocotyl tip than in the fully differentiated mesocotyl tissue. Only in the tip region did light exposure lead to a strong and coordinate down-regulation of both mRNAs whereas in the differentiated mesocotyl only a slight decrease was observed. The results indicate that expression of the 'housekeeping' V-type H+-ATPase is strongly regulated in response to growth rate.

Does a sodium-free buffer affect QRS width in experimental amitriptyline overdose?

STUDY OBJECTIVES

We carried out this study to determine the effects of pH alteration on QRS width with administration of tromethamine, a non-sodium-containing buffering agent, in experimental amitriptyline overdose.

DESIGN

Prospective, nonblinded trial.

PARTICIPANTS

Adult mongrel dogs.

INTERVENTIONS

Pentobarbital-anesthetized dogs were overdosed with amitriptyline 5 mg/kg followed by infusion at 1.0 mg/kg/minute until the QRS width doubled, then decreased to .5 mg/kg/minute until the end of the experiment. At two defined points of toxicity, the dose of tromethamine required to raise the pH to 7.50 +/- 4 was given. pH and QRS width at a speed of 100 mm/second were measured over a 30-minute period after each tromethamine dose. Data were analyzed with non-linear-regression analysis.

RESULTS

At toxicity 1 the mean pH was 7.32, with a QRS width of 11.6 mm. Two minutes after the tromethamine dose the pH rose to 7.51, with narrowing of the QRS width to 8.4 mm. At toxicity 2 the pH was 7.40, with QRS width of 10.6 mm. Two minutes after tromethamine, the pH rose to 7.49 and the QRS width decreased to 9.7 mm. Regression analysis showed a correlation between pH and QRS width; as pH increased, QRS width decreased (P = .0001).

CONCLUSION

Cardiac toxicity of amitriptyline overdose, as manifested by QRS widening, is reversible by pH changes alone.

The 1-month outcome of patients with a low probability Technegas ventilation/perfusion lung scan

The objective was to study the 1-month outcome of patients who had a low probability ventilation/perfusion lung scan using Technegas radioaerosol as the inhalational agent and who did not receive anticoagulation. One hundred consecutive patients with suspected pulmonary embolism were studied retrospectively. Their Technegas lung scans were classified by two blinded and independent nuclear medicine physicians and the medical records of all patients with a low probability scan were reviewed. One hundred inpatients (42 males and 58 females) with a mean age of 63 years were studied. The three most common clinical presentations leading to lung scintigraphy were unexplained dyspnoea (30 cases), unexplained dyspnoea with pleuritic chest pain (26 cases) and pleuritic chest pain only (15 cases). Nine patients had been judged by their managing medical team to have a high clinical probability of true pulmonary embolism, 32 had an intermediate probability clinical presentation and 59 a low clinical probability of pulmonary embolism. None of the 100 patients experienced further episodes of suspected or proven pulmonary embolism during the follow-up period. Six patients died. In none of them was pulmonary embolism either the cause of or a major contributing factor to death. The finding of a low probability scan using Technegas as the ventilation scintigram agent of choice describes a group of patients who, even in the absence of therapeutic anticoagulation, have a favourable 1-month outcome free of either true or suspected clinical pulmonary embolism. Invasive, pulmonary angiography-based diagnostic strategies may not be needed in this group of patients.

CT findings in acute renal cortical necrosis

Acute renal cortical necrosis has three characteristic findings on contrast enhanced CT: (a) lack of enhancement of the renal cortex, (b) enhancement of the renal medulla, and (c) absent renal excretion.

Alpha-smooth muscle actin in parenchymal cells of bleomycin-injured rat lung

Bleomycin causes focally diffuse interstitial fibrosis characterized by increases in the number and volume of contractile filament-laden parenchymal cells, as well as increased parenchymal contractility. However, the origin of these cells and their relationship to altered contractility, remain unknown. We now have used immunohistochemical methods to ask if cells containing smooth muscle actin and myosin are present in involved regions of parenchyma. Staining of the parenchyma of control lungs with a monoclonal antibody against alpha-smooth muscle actin is sparse, consisting of reactivity with the alveolar entrance ring (septal tip) cells as well as occasional reactivity of alveolar wall cells that may represent pericytes or contractile interstitial cells. Increased alpha-smooth muscle actin staining was observed in areas of parenchymal damage in lungs from animals sacrificed between 1 and 4 weeks postbleomycin instillation. This reactivity included altered staining of the airway and vessel smooth muscle coat as well as thickened septal tips. In addition, newly reactive cells were observed in interstitial and intraalveolar regions and in bands of thickened submesothelial tissue. Staining was most intense in the focal fibrotic lesions which are characteristic of this injury. By contrast, parenchymal reactivity with a polyclonal antibody against smooth muscle myosin at the later time points shows only a mild increase in punctate staining in the damaged foci. We hypothesize that the substantial increase in alpha-smooth muscle actin containing cells in fibrotic regions of involved parenchyma after bleomycin injury is responsible for the altered morphologic, biochemical, and mechanical properties that we have observed.

Characterization of vascular smooth muscle cell phenotype in long-term culture

Studies of bovine carotid artery smooth muscle cells, during long-term in vitro subcultivation (up to 100 population doublings), have revealed phenotypic heterogeneity among cells, as characterized by differences in proliferative behavior, cell morphology, and contractile-cytoskeletal protein profiles. In vivo, smooth muscle cells were spindle-shaped and expressed desmin and alpha-smooth muscle actin (50% of total actin) as their predominant cytoskeletal and contractile proteins. Within 24 h of culture, vimentin rather than desmin was the predominant intermediate filament protein, with little change in alpha-actin content. Upon initial subcultivation, all cells were flattened and fibroblastic in appearance with a concomitant fivefold reduction in alpha-actin content, whereas the beta and gamma nonmuscle actins predominated. In three out of four cell lines studied, fluctuations in proliferative activity were observed during the life span of the culture. These spontaneous fluctuations in proliferation were accompanied by coordinated changes in morphology and contractile-cytoskeletal protein profiles. During periods of enhanced proliferation a significant proportion of cells reverted to their original spindle-shaped morphology with a simultaneous increase in alpha-actin content (20 to 30% of total actin). These results suggest that in long-term culture smooth muscle cells undergo spontaneous modulations in cell phenotype and may serve as a useful model for studying the regulation of intracellular protein expression.

Mast cell heterogeneity and hyperplasia in bleomycin-induced pulmonary fibrosis of rats

The distribution, density, and histochemical subtype of mast cells were studied in the respiratory tract of rats with bleomycin-induced pulmonary fibrosis. In normal rats, mast cell densities were highest in the trachea and lowest in the bronchus and parenchyma. Two histochemically distinct mast cell populations were identified in the mucosa adjacent to the tracheal cartilage, but elsewhere only a single population of typical connective tissuelike mast cells was found. After intratracheally administered bleomycin, lung histamine levels (micrograms/g wet weight) increased as much as 14-fold by Day 50. Pulmonary mast cell changes were present early in the fibrotic process, and by Day 14 the mast cell density in the parenchyma was 10 times normal. These parenchymal mast cells were histochemically of the connective tissue type. Thus, pronounced mast cell hyperplasia occurs during the evolution of experimental pulmonary fibrosis. This model provides a powerful tool to study pulmonary mast cells and to identify their role in fibrotic disease.

Advance prediction of transthoracic impedance in human defibrillation and cardioversion: importance of impedance in determining the success of low-energy shocks

The purposes of this study were to evaluate a method that predicts transthoracic impedance in advance of defibrillating shocks in humans and to assess the importance of transthoracic impedance in low-energy defibrillation. Via defibrillator electrodes we applied 31 kHz current to the chest during the defibrillator charge cycle, before the defibrillating shock was actually delivered. The current flow was limited by transthoracic impedance; a microprocessor monitored the predischarge current flow and determined the predischarge impedance by calibration against known resistance values. Actual impedance to the defibrillating shock was also determined and compared with the predicted impedance. With this approach we predicted impedance in 19 patients who received 66 shocks for ventricular and atrial arrhythmias. Predicted impedance (y) correlated very well with actual impedance (x):y = .90x + 11.3; r = .97. To determine the importance of impedance in defibrillation and cardioversion, we prospectively gathered data from 96 patients who received shocks of various energies for ventricular or atrial arrhythmias. In patients with high transthoracic impedance (greater than 97 omega), low-energy shocks (less than or equal to 100 J) for ventricular defibrillation had only a 20% success rate as opposed to a 70% success rate for low-energy shocks in patients with low or average impedance (p less than .05). We conclude that transthoracic impedance can be accurately predicted in advance of defibrillation and cardioversion. This method permits the preshock identification of patients with high impedance in whom attempts to defibrillate with low-energy shocks are inappropriate.

Circadian rhythm of hourly ventricular arrhythmia frequency in man

Three twenty-four hour electrocardiographic recordings from 164 untreated patients were analyzed. A clear, statistically significant, diurnal pattern in hourly ventricular arrhythmia frequency was found. It was consistent across days and between seven diagnostic groups. A high frequency Noon to 4:00 PM peak contrasted with a low frequency 1:00 AM to 5:00 AM trough with zero hourly frequencies not uncommonly present. These findings appear applicable to large ambulatory populations and may well influence the design of future investigations of modalities which alter ventricular arrhythmia frequency.

Auditory evoked potentials compared to performance measures and EEG in assessing excessive daytime sleepiness in narcolepsy-cataplexy

The AEP to the repetitive stimuli of the Wilkinson auditory vigilance task was compared between untreated patients with narcolepsy-cataplexy and matched controls for periods during which the tones were preceded by 13 sec or more of wakefulness (defined by EEG-polygraphic criteria). During these periods it had been found previously that narcoleptics did not perform worse than did controls. The AEP, nevertheless, showed significant differences for narcoleptics. These were similar to changes described for drowsiness in normals. The AEP, therefore, showed changes related to excessive day time drowsines in narcolepsy-cataplexy when a sensitive performane measure and visual analysis of EEG-polygraphic recordings did not.

Thermodynamics of mixing of dipalmitoyl phosphatidylcholine and egg phosphatidylcholine in hydrated bilayers

Dipalmitoyl phosphatidylcholine (DPPC) and egg phosphatidylcholine (egg PC) are not completely miscible at all temperatures. Their phase diagram was determined by differential scanning calorimetry (DSC) of aqueous mixtures of the two. From the integrated DSX curves we obtained the enthalpy of solution of DPPC in egg PC delta hs, as a function of the mole fraction of DPPC, X, and using the empirical relationship between delta hs and X, the solubility Xsat as a function of temperature, T. The latter could be described by the semiempirical relationship: R1nXsat = a + blnT - c/T, where a = 6.57 X 10(-2) kcal.mol-1. degree -1 and c = 20.5 kcal. mol-1 (1 cal = 4.1868 J); the coefficient b was very small and could be ignored. The quantity delta hs can be given as XdeltahDPPC + deltah mix, where deltah DPPC is the gel - liquid crystalline transition enthalpy of DPPC (8.74 kcal.mol-1) and deltah mix is the enthalpy of mixing the two liquid crystalline lipids. Deltahmix depends on X in approximately a parabolic fashion, having a maximal value of 4.8 kcal.mol-1 at X = 0.6. It was shown that both the solubility and mixing enthalpy data can be described by the theory of regular solutions (RST). In RST, the activity coefficient of the solute (component 2) of a binary solution is given by RTIngamma 2 = (1 - Theta2)2deltaU, while the mixing enthalpy is given by delta hmix = Theta1 Theta2 delta U/v2, where Theta1 and Theta2 are the volume fractions of solvent and solute (egg PC and DPPC, respectively), v2 is the partial molar volume of DPPC, and deltaU is the energy change per mole on interchanging a DPPC and an egg PC molecule between their respective liquid crystalline phases. The thermodynamic data are accurately described by RST, the molar volume of DPPC being found to be about half that of egg PC solution and the interchange energy deltaU having a value of 10-11 kcal.mol-1. There was some evidence that deltaU may be an increasing function of temperature. The large value of the deltaU accounts for the pronounced temperature dependence of the solubility Xsat, which decreases from 0.35 at 35 degrees C to 0.02 at 10 degrees C. The presence of cholesterol in the mixtures decreases both the transition enthalpy of DPPC and the mixing enthalpy in a linear fashion, so that deltahs is zero at Xcholesterol greater than or equal to 0.2. The results are consistent with recent data including the formation of a PC-cholesterol complex oc stoichiometry approximately 4:1.

Efficacy of percutaneous transluminal coronary recanalization utilizing streptokinase thrombolysis in patients with acute myocardial infarction

Since coronary thrombosis is a principal factor in the evolving necrotic process in the majority of patients with acute myocardial infarction (AMI), a prospective study was conducted in 25 AMI patients who underwent expeditious coronary arteriography. Of these patients, 22 with totally occluding thrombus also received early streptokinase (STK) administration. STK was given by intracoronary (20 patients) or systemic (two patients) infusion, 2000 to 50,000 IU/min, to a total dose of 125,000 to 500,000 IU within 10 hours of AMI symptom onset. Eighteen patients had angiographically visualized successful coronary thrombolysis; the shorter the interval between onset of symptoms to treatment, the more rapid was the clot dissolution. Successful thrombolysis occurred concomitantly with readily managed reperfusion ventricular tachyarrhythmias in nearly all patients. In addition, STK recanalization resulted in relief of ongoing chest pain in 10 of 12 patients, 10 of 16 evidenced immediate normalization of hyperacute ST segment abnormalities, and 8 of 14 demonstrated subsequent improvement of angiographically visualized left ventricular (LV) ejection fraction. In the percutaneous transluminal coronary recanalization (PTCR) procedure, the step of using a soft-tipped guide wire itself was transiently useful in only one of seven patients in whom this was attempted; reocclusion took place without added STK therapy. Nitroglycerin (NTG) alone produced only slight distal patency in but 1 of 19 patients with coronary occlusion given the nitrate. Importantly, in 14 control AMI patients receiving conventional treatment without STK, 10 showed angiographically complete occlusion of the coronary artery supplying the infarct region 1 month after infarction, thereby excluding spontaneous clot lysis mimicking STK-PTCR-induced reperfusion. These data support the concept that coronary occlusion by thrombosis is inherently involved with AMI and that rapid PTCR application of intracoronary STK provides potent thrombolysis, superior to that provided by NTG and guide wire passage in reestablishing coronary flow with attendant salvage of jeopardized myocardium and with subsequently improved LV function.

Heterogeneous catalysis by phospholipase A2: mechanism of hydrolysis of gel phase phosphatidylcholine

Hydrolysis of gel phase dipalmitoylphosphatidylcholine (DPPC) at 37 degrees C catalysed by Crotalus atrox phospholipase A2 (PLA) is described extremely well by the "path 1" kinetic mechanism of Tinker and Wei (1979) (Can. J. Biochem. 57, 97-106), if reversible adsorption is allowed as a side reaction. Progress curves show an initial rapid phase, the initial velocity being a Michaelis-Menten function dependent on the catalytic properties of the enzyme (kcat approximately equal to 9200 min-1, Km approximately equal to 0.12 mM), then level off to a slower rate determined by the desorption equilibrium constant (KD approximately equal to 0.01 mM) and desorption rate constant (kD approximately equal to 0.15 min-1). The relaxation time, tau, for the transition to the desorption-limited reaction is approximately 0.5 min; this large value of tau probably arises from a slow conversion of active, dimeric enzyme to an inactive protein species adsorbed to the lipid surface. At later times in the reaction there is an increase in the rate of hydrolysis, attributed to a stimulation of desorption by the products. The desorption equilibrium constant KD is a quadratic function of the surface concentration of products and increases 20- to 30-fold when all accessible substrate is hydrolysed. Both lysophosphatidylcholine (lyso-PC) and fatty acid were found to stimulate the desorption, but lyso-PC was also found to be a competitive inhibitor of the catalysis. Adsorption of PLA to DPPC and egg PC vesicles was directly measured using a gel partition technique. Strong binding to egg PC was observed, which was not dependent on the presence of calcium ion (essential for catalysis); PLA inhibited by acylation of up to four lysine residues per mole of monomeric enzyme with ethoxyformic anhydride was equally strongly adsorbed, indicating that lipid binding is not dependent on catalytic activity. Reaction products greatly weakened the binding of PLA to the lipid surface as expected. Cholesterol had two effects on the hydrolytic reaction: there was a striking decrease in the rate of the slower, desorption-limited phase, the rate of which decrease to almost zero at 15 mol% cholesterol, but there was also evidence for the formation of a complex with stoichiometry 1 cholesterol: 2 DPPC in which DPPC is no longer a substrate for the enzyme. Implications of the proposed mechanism for specificity and control of surface catalysis by PLA are discussed.

Effects of oral pentaerythritol tetranitrate in cardiac failure and angina pectoris. Assessment by hemodynamic measurement and exercise capacity

Oral pentaerythritol tetranitrate produces sustained beneficial hemodynamic effects in patients with cardiac failure of varied etiology. The principle action is a reduction of elevated left ventricular filling pressure. In a small group of angina patients, the oral nitrate in high dosage resulted in considerable increase in angina-limited exercise capacity compared to placebo for four hours following drug administration. No side effects were associated with ingestion of pentaerythritol tetranitrate in these investigations.