A Three-dimensional Analysis of Flow in the Pivot Regions of an ATS Bileaflet Valve

Bileaflet heart valves are currently the most commonly implanted type of mechanical prosthetic valve, because of their low transvalvular pressure drop, centralised flow and durability. However, in common with all mechanical heart valves, implanted bileaflet valves show an inherent tendency for blood clot formation at the valve site. Fluid dynamical phenomena associated with blood clotting are elevated blood shear stresses and regions of persistent blood recirculation, particularly when both occur together. Using three-dimensional CFD modelling, combined with enlarged scale experimental modelling, we investigated the blood flow through the ATS bileaflet valve during forward flow, with particular attention to the leaflet pivot regions. Recirculating regions were found both within and downstream of the valve housing ring. Qualitative assessment of the entire cardiac cycle suggested that recirculating blood within the housing ring will be washed away whilst the valve is closed, but as with all bileaflet valve designs recirculating blood downstream of the valve may have a residence time much longer than one cardiac cycle.

Subspecialisation in Emergency Radiology: Proposal for a harmonised European curriculum

Introduction: Radiology plays a crucial role in the emergency care setting by delivering early and precise diagnoses under pressure of time, right at the beginning of patient treatment. Although there is a need for postgraduate education in emergency radiology, most of the national bodies responsible do not offer it in a uniform fashion and a general proof of qualification is missing in Europe. Therefore, the European Society of Radiology (ESR) has founded the (Sub-)Society of Emergency Radiology (ESER), prompting them to develop a European curriculum. This trend, which is currently also encouraged in many other non-radiological specialties which demand the highest professional qualifications, often lacks expertise in medical education. Goals: The goal of this article is the general description of the curricular planning process for a European postgraduate subspecialisation programme, using the example of Emergency Radiology (European Diploma in Emergency Radiology, EDER), including the utilisation of TOOLS and recommendations derived from comparable projects. Project description: The project was divided into partial steps: the timeline displayed in a GANTT chart, and tasks and responsibilities assigned in a RASCI matrix. The curriculum was iteratively developed using the KERN approach and steps were prioritised using the PARETO principle. Furthermore, the following TOOLS were used: limitations and needs assessment, SWOT analysis, formulating learning objectives and categorising them after MILLER and SCLO, and using BLOOM's taxonomy for cognitive learning objectives and operationalising them according to MAGER. Psychomotoric and affective learning objectives were assigned to CANMEDS roles, grouped by topic using CLUSTERING, and then mapped by MATRIX analysis to appropriate learning and evaluation methods. Striving for continuous improvement, the curriculum was finally embedded in curricular quality management. Results: The standardisation of the EDER access, considering the different national conditions, the minimisation of European learners' attendance phases, restricting expenses by best possible use of existing structures, respecting the requirements and retaining the support of the European umbrella society ESR, finishing the project by a specific deadline and the demands of continuous improvement were particular challenges. A curriculum with the eligibility of five years' speciality training in general radiology has evolved on schedule. The subspeciality training lasts at least one year and is divided into webinars, workshops during congresses (e.g. the annual ESR and ESER congresses) and one year practical training at the individual learner's corresponding local hospitals, which adhere to a catalogue of requirements, comparable to national educational policies. The curriculum is completed by passing a written and oral exam (diploma) and re-accreditation every five years. Conclusions: Despite complex requirements, the TOOLS utilised allowed an almost seamless, resource-minimised, professional, location-independent distributed development of a European subspeciality curriculum within one year. The definitive implementation is still due. If any deviations from the draft presented should become necessary in the future, the embedment in the curricular quality management will lead to a redirection in the right way and, furthermore, secure a continuous improvement in the best way possible.

Pregnancy-driven cardiovascular maternal miR-29 plasticity in obesity

BACKGROUND

Obesity in pregnancy (MO) is a risk factor for maternal and/or fetal cardiovascular system disorders. This study evaluated maternal CVS expression of microRNA-29 family and its target molecules in MO to test the hypotheses: CVS miR-29 concentrations are increased in pregnancy and decreased in MO.

METHODS

Non-pregnant (n=4), pregnant obese (POb, n=4), and pregnant non-obese (PnOb, n=4) baboons (Papio spp.) were studied. Maternal left ventricle (LV), left atrium (LA), and aortic arch (AA) were collected at the end of gestation. Expression of MiR-29 and elastin (ELN) mRNA were quantified.

RESULTS

LA miR-29 (a, c) expression was highest in PnOb. In the LV, miR-29b expression trended lower (P=.059) for PnOb animals. ELN mRNA expression correlated positively with miR-29b expression in AA (r=.76, P=.03).

CONCLUSION

Maternal obesity diminishes miR-29 adaptation to pregnancy. Pharmacologic, tissue-specific targeting of miRNA-29 may represent a strategy for prevention and treatment of MO complications.

Abstract 4902: A mouse GITRL fusion protein drives T-cell activation and antitumor activity in preclinical mouse models of cancer

GITR is a member of the TNFR superfamily of proteins and is expressed on resting regulatory T-cells and on other T-cells following activation. Signals through GITR have been shown to drive increased T-cell activity and reduced regulatory T-cell function. In order to explore the potential of therapeutically targeting GITR in a cancer setting, we generated a mouse GITRL fusion protein (mGITRL FP) consisting of the extracellular domain of mGITRL linked to a structural domain and an IgG Fc domain. The antitumor activity and pharmacodynamic effects of this molecule were then explored in the colorectal syngeneic model of cancer (CT26). Treatment of mice with mGITRL FP mediated anti-tumor activity that was dependent on isotype and exposure. The anti-tumor activity could be attributed at least in part to the increased activation and proliferation status of CD8+ and CD4+ T-cells, as evidenced by increases in Ki67 expression and ICOS upregulation. Intratumourally we observed a significant decrease in the frequency of CD4+ T-cells (including T regs), but a corresponding increase in cytotoxic CD8+ T-cells. OX40 is another member of the TNFR superfamily, that has similar expression and functions to GITR. In order to better understand the potential differences between targeting of these two pathways, the activity and pharmacodynamic effects of the mGITRL FP were additionally compared and contrasted to those of a mOX40L FP and the observed differences will be discussed.

Citation Format: Rebecca Leyland, Amanda Watkins, Kathy A. Mulgrew, Lisa Bamber, Natalie J. Tigue, Emily Dick, Nick Holoweckyj, Lesley Young, Michelle Morrow, Scott A. Hammond, Ching Ching Leow, Robert W. Wilkinson, Ross Stewart. A mouse GITRL fusion protein drives T-cell activation and antitumor activity in preclinical mouse models of cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4902.

Identification and Characterization of MEDI4736, an Antagonistic Anti-PD-L1 Monoclonal Antibody

Programmed cell-death 1 ligand 1 (PD-L1) is a member of the B7/CD28 family of proteins that control T-cell activation. Many tumors can upregulate expression of PD-L1, inhibiting antitumor T-cell responses and avoiding immune surveillance and elimination. We have identified and characterized MEDI4736, a human IgG1 monoclonal antibody that binds with high affinity and specificity to PD-L1 and is uniquely engineered to prevent antibody-dependent cell-mediated cytotoxicity. In vitro assays demonstrate that MEDI4736 is a potent antagonist of PD-L1 function, blocking interaction with PD-1 and CD80 to overcome inhibition of primary human T-cell activation. In vivo MEDI4736 significantly inhibits the growth of human tumors in a novel xenograft model containing coimplanted human T cells. This activity is entirely dependent on the presence of transplanted T cells, supporting the immunological mechanism of action for MEDI4736. To further determine the utility of PD-L1 blockade, an anti-mouse PD-L1 antibody was investigated in immunocompetent mice. Here, anti-mouse PD-L1 significantly improved survival of mice implanted with CT26 colorectal cancer cells. The antitumor activity of anti-PD-L1 was enhanced by combination with oxaliplatin, which resulted in increased release of HMGB1 within CT26 tumors. Taken together, our results demonstrate that inhibition of PD-L1 function can have potent antitumor activity when used as monotherapy or in combination in preclinical models, and suggest it may be a promising therapeutic approach for the treatment of cancer. MEDI4736 is currently in several clinical trials both alone and in combination with other agents, including anti-CTLA-4, anti-PD-1, and inhibitors of IDO, MEK, BRAF, and EGFR.

Endocannabinoid crosstalk between placenta and maternal fat in a baboon model (Papio spp.) of obesity

INTRODUCTION

Maternal obesity (MO) remains a serious obstetric problem with acute and chronic morbidities for both mothers and offspring. The mechanisms underlying these adverse consequences of MO remain unknown. Endocannabinoids (ECB) are neuromodulatory lipids released from adipocytes and other tissues. Metabolic crosstalk between placenta and adipocytes may mediate sequelae of MO. The goal of this study was to elucidate placental and systemic ECB in MO.

MATERIAL AND METHODS

Placentas, sera, and subcutaneous fat were collected at Cesarean sections performed near term (0.9 G) in four non-obese (nOB) and four obese (OB) baboons (Papio spp.). Concentrations of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured by liquid chromatography coupled to tandem mass spectrometry. AEA and 2-AG pathways were characterized in placentas by Q-RT-PCR, Western blot and immunohistochemistry.

RESULTS

Placental 2-AG levels were lower and maternal fat AEA levels were higher in OB (1254.1 ± 401.3 nmol/kg and 17.3 ± 4 nmol/kg) vs. nOB (3124.2 ± 557.3 nmol/kg and 3.1 ± 0.6 nmol/kg) animals. Concentrations of 2-AG correlated positively between maternal fat and placenta (r = 0.82, p = 0.013), but correlated negatively with maternal leptin concentrations (r = -0.72, p = 0.04 and r = -0.83, p = 0.01, respectively).

CONCLUSION

This is the first study to demonstrate differential ECB pathway regulation in maternal fat and placenta in MO. Differential regulation and function exist for AEA and 2-AG as the major ECB pathways in placenta.

Impact of obesity severity and duration on pancreatic β- and α-cell dynamics in normoglycemic non-human primates

OBJECTIVE

Obesity is associated with high insulin and glucagon plasma levels. Enhanced β-cell function and β-cell expansion are responsible for insulin hypersecretion. It is unknown whether hyperglucagonemia is due to α-cell hypersecretion or to an increase in α-cell mass. In this study, we investigated the dynamics of the β-cell and α-cell function and mass in pancreas of obese normoglycemic baboons.

METHODS

Pancreatic β- and α-cell volumes were measured in 51 normoglycemic baboons divided into six groups according to overweight severity or duration. Islets morphometric parameters were correlated to overweight and to diverse metabolic and laboratory parameters.

RESULTS

Relative α-cell volume (RαV) and relative islet α-cell volume (RIαV) increased significantly with both overweight duration and severity. Conversely, in spite of the induction of insulin resistance, overweight produced only modest effects on relative β-cell volume (RβV) and relative islet β-cell volume (RIβV). Of note, RIβV did not increase neither with overweight duration nor with overweight severity, supposedly because of the concomitant, greater increase in RIαV. Baboons' body weights correlated with serum levels of interleukin-6 and tumor necrosis factor-α soluble receptors, demonstrating that overweight induces abnormal activation of the signaling of two cytokines known to impact differently β- and α-cell viability and replication.

CONCLUSION

In conclusion, overweight and insulin resistance induce in baboons a significant increase in α-cell volumes (RαV, RIαV), whereas have minimal effects on the β cells. This study suggests that an increase in the α-cell mass may precede the loss of β cells and the transition to overt hyperglycemia and diabetes.

Exon skipping and gene transfer restore dystrophin expression in human induced pluripotent stem cells-cardiomyocytes harboring DMD mutations

With an incidence of ∼1:3,500 to 5,000 in male children, Duchenne muscular dystrophy (DMD) is an X-linked disorder in which progressive muscle degeneration occurs and affected boys usually die in their twenties or thirties. Cardiac involvement occurs in 90% of patients and heart failure accounts for up to 40% of deaths. To enable new therapeutics such as gene therapy and exon skipping to be tested in human cardiomyocytes, we produced human induced pluripotent stem cells (hiPSC) from seven patients harboring mutations across the DMD gene. Mutations were retained during differentiation and analysis indicated the cardiomyocytes showed a dystrophic gene expression profile. Antisense oligonucleotide-mediated skipping of exon 51 restored dystrophin expression to ∼30% of normal levels in hiPSC-cardiomyocytes carrying exon 47-50 or 48-50 deletions. Alternatively, delivery of a dystrophin minigene to cardiomyocytes with a deletion in exon 35 or a point mutation in exon 70 allowed expression levels similar to those seen in healthy cells. This demonstrates that DMD hiPSC-cardiomyocytes provide a novel tool to evaluate whether new therapeutics can restore dystrophin expression in the heart.

Exon skipping and gene transfer restore dystrophin expression in hiPSC-cardiomyocytes harbouring DMD mutations

With an incidence of ~1:3,500 to 5,000 in male children, Duchenne muscular dystrophy (DMD) is an X-linked disorder in which progressive muscle degeneration occurs and affected boys usually die in their twenties or thirties. Cardiac involvement occurs in 90% of patients and heart failure accounts for up to 40% of deaths. To enable new therapeutics such as gene therapy and exon skipping to be tested in human cardiomyocytes, we produced human induced pluripotent stem cells (hiPSC) from seven patients harbouring mutations across the DMD gene. Mutations were retained during differentiation and analysis indicated the cardiomyocytes showed a dystrophic gene expression profile. Antisense oligonucleotide-mediated skipping of exon 51 restored dystrophin expression to ~30% of normal levels in hiPSC-cardiomyocytes carrying exon 47-50 or 48-50 deletions. Alternatively, delivery of a dystrophin minigene to cardiomyocytes with a deletion in exon 35 or a point mutation in exon 70 allowed expression levels similar to those seen in healthy cells. This demonstrates that DMD hiPSC-cardiomyocytes provide a novel tool to evaluate whether new therapeutics can restore dystrophin expression in the heart.

Abruptio placentae in cynomolgus macaques (Macaca fascicularis): male bias

BACKGROUND

Abruptio placentae is a serious problem with a high rate of maternal and fetal mortality and documented sexual dimorphism in reoccurrence. Macaca fascicularis is a well-described reproductive model; however, there are no data available regarding sexual dimorphism in abruptio placentae in these species.

METHODS

A retrospective study of pathology and medical records in a large colony of M. fascicularis was performed. Placental specimens were analyzed.

RESULTS

The incidence of placenta abruptio in the colony was 15.7/1000 births. In the abruptio placentae group, male fetuses had lower placental disk length and increased femur length compared with female fetuses. The feto-pacental ratio and fetal weight were lower in the male fetuses in the abruption group compared with those in the stillbirth group without abruption placentae.

CONCLUSION

This is the first documentation of male bias in placental and fetal development in abruptio placentae in non-human primates.

Recurrent abruptio placentae in a cynomolgus monkey (Macaca fascicularis)

INTRODUCTION

Abruptio placentae, defined as premature separation of a normally implanted placenta, is a life threatening pregnancy complication with unknown pathophysiology. A history of abruptio placentae is the major risk factor for this pregnancy complication in humans. We describe the first case of recurrent abruptio placentae in a Macaca fascicularis.

MATERIAL AND METHODS

A pregnant M. fascicularis at term gestation was presented with weakness and hypothermia. Cesarean section revealed retroplacental hemorrhage with partial placental separation from the uterus.

RESULTS

The weight of the female fetus was within the lower birth weight range for these species. The maternal side of placenta contained necrotic tissue, occupying approximately 60% of the maternal surface. The placental implantation bed demonstrated neutrophil infiltration. Perivascular collections of lymphocytes were noticed in the uterine smooth muscle.

CONCLUSION

This case report underlines the importance of neutrophil infiltration and uterine venous drainage in the cascade of events leading to abruptio placentae.

Do semantic categories activate distinct cortical regions? Evidence for a distributed neural semantic system

A key issue in cognitive neuroscience concerns the neural representation of conceptual knowledge. Currently, debate focuses around the issue of whether there are neural regions specialised for the processing of specific semantic attributes or categories, or whether concepts are represented in an undifferentiated neural system. Neuropsychological studies of patients with selective semantic deficits and previous neuroimaging studies do not unequivocally support either account. We carried out a PET study to determine whether there is any regional specialisation for the processing of concepts from different semantic categories using picture stimuli and a semantic categorisation task. We found robust activation of a large semantic network extending from left inferior frontal cortex into the inferior temporal lobe and including occipital cortex and the fusiform gyrus. The only category effect that we found was additional activation for animals in the right occipital cortex, which we interpret as being due to the extra visual processing demands required in order to differentiate one animal from another. We also carried out analyses in specific cortical regions that have been claimed to be preferentially activated for various categories, but found no evidence of any differential activation as a function of category. We interpret these data within the framework of cognitive accounts in which conceptual knowledge is represented within a nondifferentiated distributed system.

Directed differentiation of human embryonic stem cells to interrogate the cardiac gene regulatory network

The limited ability of the heart to regenerate has prompted development of new systems to produce cardiomyocytes for therapeutics. While differentiation of human embryonic stem cells (hESCs) into cardiomyocytes has been well documented, the process remains inefficient and/or expensive, and progress would be facilitated by better understanding the early genetic events that cause cardiac specification. By maintaining a transgenic cardiac-specific MYH6-monomeric red fluorescent protein (mRFP) reporter hESC line in conditions that promote pluripotency, we tested the ability of combinations of 15 genes to induce cardiac specification. Screening identified GATA4 plus TBX5 as the minimum requirement to activate the cardiac gene regulatory network and produce mRFP(+) cells, while a combination of GATA4, TBX5, NKX2.5, and BAF60c (GTNB) was necessary to generate beating cardiomyocytes positive for cTnI and α-actinin. Including the chemotherapeutic agent, Ara-C, from day 10 of induced differentiation enriched for cTnI/α-actinin double positive cells to 45%. Transient expression of GTNB for 5-7 days was necessary to activate the cardiogenesis through progenitor intermediates in a manner consistent with normal heart development. This system provides a route to test the effect of different factors on human cardiac differentiation and will be useful in understanding the network failures that underlie disease phenotypes.

Drug evaluation in cardiomyocytes derived from human induced pluripotent stem cells carrying a long QT syndrome type 2 mutation

AIMS

Congenital long QT syndromes (LQTSs) are associated with prolonged ventricular repolarization and sudden cardiac death. Limitations to existing clinical therapeutic management strategies prompted us to develop a novel human in vitro drug-evaluation system for LQTS type 2 (LQT2) that will complement the existing in vitro and in vivo models.

METHODS AND RESULTS

Skin fibroblasts from a patient with a KCNH2 G1681A mutation (encodes I(Kr) potassium ion channel) were reprogrammed to human induced pluripotent stem cells (hiPSCs), which were subsequently differentiated to functional cardiomyocytes. Relative to controls (including the patient's mother), multi-electrode array and patch-clamp electrophysiology of LQT2-hiPSC cardiomyocytes showed prolonged field/action potential duration. When LQT2-hiPSC cardiomyocytes were exposed to E4031 (an I(Kr) blocker), arrhythmias developed and these presented as early after depolarizations (EADs) in the action potentials. In contrast to control cardiomyocytes, LQT2-hiPSC cardiomyocytes also developed EADs when challenged with the clinically used stressor, isoprenaline. This effect was reversed by β-blockers, propranolol, and nadolol, the latter being used for the patient's therapy. Treatment of cardiomyocytes with experimental potassium channel enhancers, nicorandil and PD118057, caused action potential shortening and in some cases could abolish EADs. Notably, combined treatment with isoprenaline (enhancers/isoprenaline) caused EADs, but this effect was reversed by nadolol.

CONCLUSIONS

Findings from this paper demonstrate that patient LQT2-hiPSC cardiomyocytes respond appropriately to clinically relevant pharmacology and will be a valuable human in vitro model for testing experimental drug combinations.

Two new protocols to enhance the production and isolation of human induced pluripotent stem cell lines

There are two critical stages in the retroviral reprogramming of somatic cells to produce human induced pluripotent stem cell (hiPSC) lines. One is the production of high titer virus required to reprogram somatic cells; the other is identification of true hiPSC colonies from heterogeneous cell populations, and their isolation and expansion to generate a sustainable, pluripotent stem cell line. Here we describe simple, time-saving methods to address the current difficulties at these two critical junctures. First, we have developed a method to increase the number of infectious viral units 600-fold. Second, we have developed a TRA-1-81-based positive selection column method for isolating "true" hiPSCs from the heterogeneous cell populations, which overcomes the labor-intensive and highly subjective method of manual selection of hiPSC colonies. We have used these techniques to produce 8 hiPSC lines from human fibroblasts and we believe that they are of considerable utility to researchers in the hiPSC field.

Ductal Plate Malformation in a Nonhuman Primate

During necropsy of a 6-year-old, male African Green monkey ( Cercopithecus aethiops), multifocal pale, white to tan areas, 1–2 cm in diameter, were noted in the right lateral lobe, medial lobe, and capsular surface of the liver. Light microscopic examination of the liver revealed numerous spindle cells dispersed within interconnecting, broad bands of collagen, up to 200 μm in width, which often spanned and connected portal areas. A diagnosis of hepatic ductal plate malformation, most closely resembling congenital hepatic fibrosis with von Meyenburg complexes, was made. Few cases of ductal plate malformations in domestic animals are reported in the literature. To our knowledge, this is the first case reported in a nonhuman primate.

Objects and their actions: evidence for a neurally distributed semantic system

An influential model of conceptual knowledge claims that objects are represented in a distributed network of cortical areas that store information about different types of attributes, such as form, colour, and motion (A. Martin et al., 2000, in: The Cognitive Neurosciences, 2nd ed., MIT Press, Cambridge). Two specific claims of this account are that (a) the motions and actions associated with objects (along with other attributes) are automatically activated whenever the object concept is evoked and (b) topographically distinct neural regions are responsible for motion/action attributes pertaining to objects in the categories of tools and animals. We used fMRI to examine the neural activation associated with conceptual processing of nouns referring to animals and tools and for verbs referring to tool-associated actions (e.g., drilling, painting) and biological actions (e.g., walking, jumping). We found that object names and their associated actions activated the same set of neural regions (left fusiform gyrus, superior and middle temporal cortex) consistent with the claim that word tool and animal concepts implicitly activate the actions associated with them. However, there was no evidence of category specificity for either objects or actions, with essentially the same activations for the form and motion attributes of both living and nonliving categories.

Computer simulation of intraventricular flow and pressure gradients during diastole

A two-dimensional axisymmetric computer model is developed for the simulation of the filling flow in the left ventricle (LV). The computed results show that vortices are formed during the acceleration phases of the filling waves. During the deceleration phases these are amplified and convected into the ventricle. The ratio of the maximal blood velocity at the mitral valve (peak E velocity) to the flow wave propagation velocity (WPV) of the filling wave is larger than 1. This hemodynamic behavior is also observed in experiments in vitro (Steen and Steen, 1994, Cardiovasc. Res., 28, pp. 1821-1827) and in measurements in vivo with color M-mode Doppler echocardiography (Stugaard et al., 1994, J. Am. Coll. Cardiol., 24, 663-670). Computed intraventricular pressure profiles are similar to observed profiles in a dog heart (Courtois et al., 1988, Circulation, 78, pp. 661-671). The long-term goal of the computer model is to study the predictive value of noninvasive parameters (e.g., velocities measured with Doppler echocardiography) on invasive parameters (e.g., pressures, stiffness of cardiac wall, time constant of relaxation). Here, we show that higher LV stiffness results in a smaller WPV for a given peak E velocity. This result may indicate an inverse relationship between WPV and LV stiffness, suggesting that WPV may be an important noninvasive index to assess LV diastolic stiffness, LV diastolic pressure and thus atrial pressure (preload).

A three-dimensional analysis of flow in the pivot regions of an ATS bileaflet valve

Bileaflet heart valves are currently the most commonly implanted type of mechanical prosthetic valve, because of their low transvalvular pressure drop, centralised flow and durability. However, in common with all mechanical heart valves, implanted bileaflet valves show an inherent tendency for blood clot formation at the valve site. Fluid dynamical phenomena associated with blood clotting are elevated blood shear stresses and regions of persistent blood recirculation, particularly when both occur together. Using three-dimensional CFD modelling, combined with enlarged scale experimental modelling, we investigated the blood flow through the ATS bileaflet valve during forward flow, with particular attention to the leaflet pivot regions. Recirculating regions were found both within and downstream of the valve housing ring. Qualitative assessment of the entire cardiac cycle suggested that recirculating blood within the housing ring will be washed away whilst the valve is closed, but as with all bileaflet valve designs recirculating blood downstream of the valve may have a residence time much longer than one cardiac cycle.

Left-ventricular pressure gradients: a computer-model simulation

Both invasive left-ventricular pressure measurements and non-invasive colour M-mode echographic measurements have shown the existence of intraventricular pressure gradients (IVPGs) during early filling. The mechanisms responsible for these IVPG cannot be completely explained by the experiments. Therefore a one-dimensional numerical model is developed and validated. The model describes filling (both velocities and pressures) along a left ventricular (LV) base-apex axis. Blood-wall interaction in the left ventricle with moving boundaries is taken into account. The computational results for a canine heart indicate that the observed IVPGs during filling are the consequence of a complex interaction between, on the one hand, pressure waves travelling in the LV and, on the other hand, LV geometry, relaxation and compliance. The computational results indicate the pressure dependency of wavespeed (0.77-1.90 m-1 s) for different mean intraventricular pressures (0.88-5.00 mmHg) and IVPGs up to 2 mmHg, independent of the ratio of end systolic volume and equilibrium volume. Increasing relaxation rate not only decreases minimum basal pressure (2.8 instead of 3.6 mmHg) but also has a strong influence on the time delay between the minimum basal and apical pressures (14 ms instead of 49 ms). The results sustain the hypothesis that pressure-wave propagation determines IVPGs and that IVPGs are no proof of elastic recoil.

Use of the mouse for the isolation and investigation of stomach-associated, spiral-helical shaped bacteria from man and other animals

Spiral-helical shaped bacteria other than Campylobacter pylori have been shown to infect the human stomach. The characteristic helical morphology of these bacteria appears to be similar to that of bacteria found in the stomachs of many other animal species. Early reports on gastric bacteria suggested that rodents may be useful for investigation and isolation of stomach-associated bacteria. Therefore, anaesthetised mice were given, through a stomach tube, a heavy suspension of a spiral-helical bacterium from a cat, scrapings of gastric mucus from primates, or a homogenised whole-antral biopsy from a human patient. At intervals after inoculation, gastric biopsies were examined by lightmicroscopy and electronmicroscopy for the presence of spiral-helical bacteria. Significant colonisation was observed in 40% of mice 1 week, and in 80% of mice 11 weeks, after inoculation with suspensions of the cat isolate. Mice were also successfully colonised by spiral bacteria present in homogenised human biopsy material and by other spiral bacteria from a monkey. These observations suggest that mice may prove to be useful animals for the study of gastric bacteria that are, as yet, non-cultivable and for analysis of some of the attributes commonly thought to be involved in colonisation.

Non Campylobacter pylori spiral organisms in the gastric antrum

Colonisation of the human gastric antrum with non Campylobacter pylori spiral organisms is described. A moderately severe histological gastritis was present despite the fact that these organisms, in contrast to C. pylori, were not closely associated with the epithelial cell surface. Although in vitro culture of the organisms was unsuccessful, in vivo culture was achieved in the mouse stomach. Further study of these spiral organisms should provide important clues to the role of bacteria in upper gastrointestinal disease.

The effect of parainfluenza 3 infection on guinea pig basophil and lung mast cell histamine release

The guinea pig infected with parainfluenza 3 (P-3) has provided an animal model to study mechanisms of virus-induced asthma and airway hyperreactivity. Evidence to identify the mechanisms by which P-3 infection enhances airway hyperreactivity, however, has not been established. The present study evaluated the effect of P-3 infection on histamine release (HR) from isolated peripheral blood guinea pig basophils and lung mast cells. Basophil HR was determined in animals made basophilic with 13 daily intraperitoneal injections of sheep blood. On Day 10 of the sensitization, blood was obtained from all animals, and leukocyte HR was determined to sheep gammaglobulin (SG), which served as the secretagogue. After these baseline studies, the animals were separated into two groups; one was insufflated with P-3 virus and the other with growth medium that did not contain virus. Four days later, animals were killed, basophils and lung mast cells were isolated, HR was determined, and lung tissue was cultured for the presence of virus. In basophils isolated from animals proven to be infected with P-3 virus, we found significantly more histamine released in response to the lower doses of SG and a significant shift in the -log EC50 dose of this antigen causing HR in these cells. Experiments conducted with the calcium ionophore A23187 as the basophil secretagogue in the same experimental design did not demonstrate similar HR findings. Furthermore, a defect in calcium disposition did not account for the enhanced HR from basophils isolated from infected animals. HR from pulmonary mast cells was similar in cells isolated from P-3-infected and control insufflated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of glucose-1,6-bisphosphate and IMP-activated glucose bisphosphatase in brain and retina

The activity of glucose-1,6-bisphosphatase and the level of its substrate were measured in 16 gray areas and four fiber areas of mouse brain and 10 layers or sublayers of monkey retina. Because of the low activity of the enzyme and the small sample sizes, it was necessary to develop a method with two different amplification steps (overall amplification about 10(6]. The enzyme ranged in activity 100-fold from a low in monkey retina photoreceptor cells to a high in the pyramidal layer of the hippocampus. However, in gray areas of the brain proper the range was only about fourfold. This, together with its requirement for IMP, suggests that the enzyme has a widespread metabolic function related to states of increased neuronal activity. Glucose-1,6-bisphosphate levels varied from 80 to 960 mu mol/kg dry weight in different areas of mouse brain and from 44 to 200 mu mol/kg dry weight in different layers of monkey retina. In general, the glucose bisphosphate levels correlated positively with the bisphosphatase activities; however, the three areas with the highest enzyme concentrations did not fit this pattern.

Extracellular K+ activity changes related to electroretinogram components. II. Rabbit (E-type) retinas

Electroretinogram (ERG) and extracellular potassium activity (K+o) measurements were carried out in isolated superfused rabbit eyecup preparations under control conditions and during the application of pharmacological agents that selectively modify the light-responsive retinal network. Light-evoked K+o changes in the rabbit (E-type) retina resemble those previously described in amphibian (I-type) retinas. Different components of the light-evoked K+o changes can be distinguished on the bases of retinal depth, V vs. log I properties, and their responses to pharmacological agents. We find two separable sources of light-evoked increases in extracellular K+: a proximal source and a distal source. The properties of the distal light-evoked K+o increase are consistent with the hypothesis that it initiates a K+-mediated current through Müller cells that is detected as the primary voltage of the electroretinographic b-wave. These experiments also support previous studies indicating that both the corneal-positive component of c-wave and the corneal-negative slow PIII potential result from K+-mediated influences on, respectively, the retinal pigment epithelium and Müller cells.

Extracellular K+ activity changes related to electroretinogram components. I. Amphibian (I-type) retinas

Electroretinographic (ERG) and extracellular potassium activity measurements were carried out in superfused eyecup preparations of several amphibians. Light-evoked changes in extracellular K+ activity were characterized on the bases of depth profile analysis and latency measurements and through the application of pharmacological agents that have selective actions on the retinal network. Three different extracellular potassium modulations evoked at light onset were identified and characterized according to their phenomenological and pharmacological properties. These modulations include two separable sources of light-evoked increases in extracellular K+: (a) a proximal source that is largely post-bipolar in origin, and (b) a distal source that is primarily or exclusively of depolarizing bipolar cell origin. The pharmacological properties of the distal extracellular potassium increase closely parallel those of the b-wave. A distal light-evoked decrease in extracellular potassium appears to be associated with the slow PIII potential, based on a combination of simultaneous intracellular Müller cell recordings and extracellular ERG and potassium activity measurements before and during pharmacological isolation of the photoreceptor responses. The extracellular potassium activity increases are discussed with respect to the Müller cell theory of b-wave generation.

Professional isolation in oncology and hospice care. Does a social work support group help?

Four social workers in hospice and oncology settings in Albany, New York formed a support group to deal with mutual problems of professional isolation, role definitions, relationships, and the stresses of working with dying patients and their families. The development, goals, and accomplishments of the group are described.

Enzymes of energy metabolism in the mudpuppy retina

The distributions of glycogen phosphorylase, hexokinase, phosphofructokinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, citrate synthase, malate dehydrogenase, beta-hydroxyacyl CoA dehydrogenase, and adenylokinase were determined in the mudpuppy retina. Distinct differences were found in regard to the glycolytic and oxidative capacities of the various layers. In the outer retina, citric acid cycle enzymes were high while glycolytic enzymes were low. Synaptic zones were distinctly enriched in all energy-producing enzymes. Mudpuppy photoreceptors were found to be rich in phosphorylase but poor in glucose-6-phosphate dehydrogenase, suggestive of some evolutionary divergence from mammals in the metabolic machinery which is used to support the visual process.

Distribution of glycine, gamma-aminobutyric acid, glutamate decarboxylase, and gamma-aminobutyric acid transaminase in rabbit and mudpuppy retinas

The distributions of glycine, gamma-aminobutyric acid (GABA), glutamate decarboxylase (EC 4.1.1.15), and GABA transaminase (EC 2.6.1.19) were determined in rabbit and mudpuppy retinas. In both species, peak levels of the amino acids and the enzymes occurred in the inner plexiform layer. Glutamate decarboxylase was almost entirely confined to the inner plexiform layer. Determinations were also made of the GABA content of 107 individual putative amacrine cell somas from mudpuppy retina. About 30% of those somas were found to have high endogenous GABA levels.

Clinical implications of research on the mechanism of action of lithium

Lithium is a unique drug in its clinical profile in psychiatry. Lithium has numerous biochemical effects, but none has yet been proven to be its mode of therapeutic action. Inhibition of noradrenaline-sensitive adenylate cyclase is reviewed as the only biochemical effect of lithium shown to occur in both animals and man at therapeutic lithium concentrations. A tetracycline antibiotic, demeclocycline, also blocks noradrenaline-sensitive adenylate cyclase. A clinical trial of demeclocycline in mania would provide a test of the adenylate cyclase theory of lithium action.

Peptides influence retinal ganglion cells

Neurotensin, substance P and (D-Ala2, Met5)-enkephalinamide were iontophoresed onto ganglion cells of the amphibian retina. Substance P and neurotensin were found to be excitatory while (D-Ala2, Met5)-enkephalinamide suppressed all types of ganglion cells. These findings are consistent with a functional role for peptides in the vertebrate retina.

[The hypnotic effect of fentanyl and sulfentanil. An electro-encephalographic comparison (author's transl)]

1. Electroencephalographic activity was registered in healthy subjects before, during and 90 minutes after intravenous injections of sufentanil and fentanyl. 2. With a dosage of ratio of 1:10, i.e., 0.025 mg/70 kg body weight sufentanil: 0.25 mg/70 kg body weight fentanyl as well as 0.015 mg/70 kg body weight sufentanil: 0.15 mg/70 kg body weight fentanyl, sufentanil was hypnotically more potent from fentanyl. 3. Sufentanil acts more powerfully on the respiratory regulation than does fentanyl. Periods of apnoea occur more frequently but can be interrupted by external psychophysiological stimulation. 4. The evaluation of indices of certain EEG-waves, characterizing well defined electroencephalographic stages corresponding to the waking-sleeping-behaviour confirmed the visual over-all analysis of the EEG-stages. 5. Physiological observations on heartrate, systemic blood pressure, rapid eye movements during wakefulness, and slow eye movements during sleepiness showed no reliable differences between sufentanil and fentanil. The systematically documented symptoms and vegetative signs of subjects also showed neither differences nor side-effects.