Aneurysmal growth in type-B aortic dissection: assessing the impact of patient-specific inlet conditions on key haemodynamic indices

Type-B aortic dissection is a cardiovascular disease in which a tear develops in the intimal layer of the descending aorta, allowing pressurized blood to delaminate the layers of the vessel wall. In medically managed patients, long-term aneurysmal dilatation of the false lumen (FL) is considered virtually inevitable and is associated with poorer disease outcomes. While the pathophysiological mechanisms driving FL dilatation are not yet understood, haemodynamic factors are believed to play a key role. Computational fluid dynamics (CFD) and 4D-flow MRI (4DMR) analyses have revealed correlations between flow helicity, oscillatory wall shear stress and aneurysmal dilatation of the FL. In this study, we compare CFD simulations using a patient-specific, three-dimensional, three-component inlet velocity profile (4D IVP) extracted from 4DMR data against simulations with flow rate-matched uniform and axial velocity profiles that remain widely used in the absence of 4DMR. We also evaluate the influence of measurement errors in 4DMR data by scaling the 4D IVP to the degree of imaging error detected in prior studies. We observe that oscillatory shear and helicity are highly sensitive to inlet velocity distribution and flow volume throughout the FL and conclude that the choice of IVP may greatly affect the future clinical value of simulations.

The Influence of Minor Aortic Branches in Patient-Specific Flow Simulations of Type-B Aortic Dissection

Type-B aortic dissection (TBAD) is a disease in which a tear develops in the intimal layer of the descending aorta forming a true lumen and false lumen (FL). Because disease outcomes are thought to be influenced by haemodynamic quantities such as pressure and wall shear stress (WSS), their analysis via numerical simulations may provide valuable clinical insights. Major aortic branches are routinely included in simulations but minor branches are virtually always neglected, despite being implicated in TBAD progression and the development of complications. As minor branches are estimated to carry about 7-21% of cardiac output, neglecting them may affect simulation accuracy. We present the first simulation of TBAD with all pairs of intercostal, subcostal and lumbar arteries, using 4D-flow MRI (4DMR) to inform patient-specific boundary conditions. Compared to an equivalent case without minor branches, their inclusion improved agreement with 4DMR velocities, reduced time-averaged WSS (TAWSS) and transmural pressure and elevated oscillatory shear in regions where FL dilatation and calcification were observed in vivo. Minor branch inclusion resulted in differences of 60-75% in these metrics of potential clinical relevance, indicating a need to account for minor branch flow loss if simulation accuracy is sought.

The Effects of Collaborative Communication Methods on Interprofessional Students’ Discharge Decision Making: A Quasi-Experimental Study

Date Presented 04/05/19

This quasi-experimental study with two groups examined the effects of face-to-face communication and written communication (documentation review) among OT, PT, and physician assistant students who made discharge decisions for a standardized patient in acute care. The findings advance the knowledge of the influences on effective communication among healthcare teams, how decision making differs between professions, and considerations for curricular planning.

Primary Author and Speaker: Young Joo Kim

Additional Authors and Speakers: Jennifer Radloff, Lynne Murphy, Christine Lysaght, C Stokes, Chia-Cheng Lin

Rare human nicotinic acetylcholine receptor α4 subunit (CHRNA4) variants affect expression and function of high-affinity nicotinic acetylcholine receptors

Nicotine, the primary psychoactive component in tobacco smoke, produces its behavioral effects through interactions with neuronal nicotinic acetylcholine receptors (nAChRs). α4β2 nAChRs are the most abundant in mammalian brain, and converging evidence shows that this subtype mediates the rewarding and reinforcing effects of nicotine. A number of rare variants in the CHRNA4 gene that encode the α4 nAChR subunit have been identified in human subjects and appear to be underrepresented in a cohort of smokers. We compared three of these variants (α4R336C, α4P451L, and α4R487Q) to the common variant to determine their effects on α4β2 nAChR pharmacology. We examined [(3)H]epibatidine binding, interacting proteins, and phosphorylation of the α4 nAChR subunit with liquid chromatography and tandem mass spectrometry (LC-MS/MS) in HEK 293 cells and voltage-clamp electrophysiology in Xenopus laevis oocytes. We observed significant effects of the α4 variants on nAChR expression, subcellular distribution, and sensitivity to nicotine-induced receptor upregulation. Proteomic analysis of immunopurified α4β2 nAChRs incorporating the rare variants identified considerable differences in the intracellular interactomes due to these single amino acid substitutions. Electrophysiological characterization in X. laevis oocytes revealed alterations in the functional parameters of activation by nAChR agonists conferred by these α4 rare variants, as well as shifts in receptor function after incubation with nicotine. Taken together, these experiments suggest that genetic variation at CHRNA4 alters the assembly and expression of human α4β2 nAChRs, resulting in receptors that are more sensitive to nicotine exposure than those assembled with the common α4 variant. The changes in nAChR pharmacology could contribute to differences in responses to smoked nicotine in individuals harboring these rare variants.

Practicing medicine without borders: tele-consultations and tele-mentoring for improving paediatric care in a conflict setting in Somalia?

OBJECTIVES

In a district hospital in conflict-torn Somalia, we assessed (i) the impact of introducing telemedicine on the quality of paediatric care, and (ii) the added value as perceived by local clinicians.

METHODS

A 'real-time' audio-visual exchange of information on paediatric cases (Audiosoft Technologies, Quebec, Canada) took place between clinicians in Somalia and a paediatrician in Nairobi. The study involved a retrospective analysis of programme data, and a perception study among the local clinicians.

RESULTS

Of 3920 paediatric admissions, 346 (9%) were referred for telemedicine. In 222 (64%) children, a significant change was made to initial case management, while in 88 (25%), a life-threatening condition was detected that had been initially missed. There was a progressive improvement in the capacity of clinicians to manage complicated cases as demonstrated by a significant linear decrease in changes to initial case management for meningitis and convulsions (92-29%, P = 0.001), lower respiratory tract infection (75-45%, P = 0.02) and complicated malnutrition (86-40%, P = 0.002). Adverse outcomes (deaths and lost to follow-up) fell from 7.6% in 2010 (without telemedicine) to 5.4% in 2011 with telemedicine (30% reduction, odds ratio 0.70, 95% CI: 0.57-0.88, P = -0.001). The number needed to be treated through telemedicine to prevent one adverse outcome was 45. All seven clinicians involved with telemedicine rated it to be of high added value.

CONCLUSION

The introduction of telemedicine significantly improved quality of paediatric care in a remote conflict setting and was of high added value to distant clinicians.

Rearing environment affects development of the immune system in neonates

Early-life exposure to appropriate microbial flora drives expansion and development of an efficient immune system. Aberrant development results in increased likelihood of allergic disease or increased susceptibility to infection. Thus, factors affecting microbial colonization may also affect the direction of immune responses in later life. There is a need for a manipulable animal model of environmental influences on the development of microbiota and the immune system during early life. We assessed the effects of rearing under low- (farm, sow) and high-hygiene (isolator, milk formula) conditions on intestinal microbiota and immune development in neonatal piglets, because they can be removed from the mother in the first 24 h for rearing under controlled conditions and, due to placental structure, neither antibody nor antigen is transferred in utero. Microbiota in both groups was similar between 2 and 5 days. However, by 12-28 days, piglets reared on the mother had more diverse flora than siblings reared in isolators. Dendritic cells accumulated in the intestinal mucosa in both groups, but more rapidly in isolator piglets. Importantly, the minority of 2-5-day-old farm piglets whose microbiota resembled that of an older (12-28-day-old) pig also accumulated dendritic cells earlier than the other farm-reared piglets. Consistent with dendritic cell control of T cell function, the effects on T cells occurred at later time-points, and mucosal T cells from high-hygiene, isolator pigs made less interleukin (IL)-4 while systemic T cells made more IL-2. Neonatal piglets may be a valuable model for studies of the effects of interaction between microbiota and immune development on allergy.

Lower filamentation rates of Candida dubliniensis contribute to its lower virulence in comparison with Candida albicans

Candida albicans and C. dubliniensis are very closely related yeast species. In this study, we have conducted a thorough comparison of the ability of the two species to produce hyphae and their virulence in two infection models. Under all induction conditions tested C. albicans consistently produced hyphae more efficiently than C. dubliniensis. In the oral reconstituted human epithelial model, C. dubliniensis isolates grew exclusively in the yeast form, while the C. albicans strains produced abundant hyphae that invaded and caused significant damage to the epithelial tissue. In the oral-intragastric infant mouse infection model, C. dubliniensis strains were more rapidly cleared from the gastrointestinal tract than C. albicans. Immunosuppression of Candida-infected mice caused dissemination to internal organs by both species, but C. albicans was found to be far more effective at dissemination than C. dubliniensis. These data suggest that a major reason for the comparatively low virulence of C. dubliniensis is its lower capacity to produce hyphae.

Early immunological changes associated with laryngeal transplantation in a major histocompatibility complex-matched pig model

Laryngeal transplantation is an increasingly viable proposition for patients with irreversible diseases of the larynx. One human transplant has been performed successfully, but many questions remain before routine transplantation can begin. In order to measure the immunological changes in mismatched transplants, it is first necessary to know the immediate combined effects of ischaemia-reperfusion injury (IRI) plus the added insult of major surgery in a fully matched setting. We measured the changes in immunologically active mucosal cells following 3 h of cold ischaemia and 8 h of in situ reperfusion in a major histocompatibility complex (MHC)-matched minipig model (n = 4). Biopsies were prepared for quantitative, multiple-colour immunofluorescence histology. The number of immunologically active cells was significantly altered above (supraglottis) and below (subglottis) the vocal cords following transplantation and reperfusion (P < 0.05, P < 0.001, respectively). However, the direction of the change differed between the two subsites: cell numbers decreased post-transplant in the supraglottis and increased in the subglottis. Despite the statistical evidence for IRI, these changes were less than the large normal inter- and intrapig variation in cell counts. Therefore, the significance of IRI in exacerbating loss of function or rejection of a laryngeal allograft is open to question. Longer-term studies are required.

The development of the mucosal immune system pre- and post-weaning: balancing regulatory and effector function

The mucosal immune system fulfils the primary function of defence against potential pathogens that may enter across vulnerable surface epithelia. However, a secondary function of the intestinal immune system is to discriminate between pathogen-associated and 'harmless' antigens, expressing active responses against the former and tolerance to the latter. Control of immune responses appears to be an active process, involving local generation of IgA and of regulatory and/or regulated T lymphocytes. Two important periods of maximum exposure to novel antigens occur in the young animal, immediately after birth and at weaning. In both cases the antigenic composition of the intestinal contents can shift suddenly, as a result of a novel diet and of colonisation by novel strains and species of bacteria. Changes in lifestyles of man, and husbandry of animals, have resulted in weaning becoming much more abrupt than previously in evolution, increasing the number of antigens that must be simultaneously evaluated by neonates. Thus, birth and weaning are likely to represent hazard and critical control points in the development of appropriate responses to pathogens and harmless dietary and commensal antigens. Neonates are born with relatively undeveloped mucosal immune systems. At birth this factor may prevent both expression of active immune responses and development of tolerance. However, colonisation by intestinal flora expands the mucosal immune system in antigen-specific and non-specific ways. At weaning antibody to fed proteins can be detected, indicating active immune responses to fed proteins. It is proposed that under normal conditions the ability of the mucosal immune system to mount active responses to foreign antigens develops simultaneously with the ability to control and regulate such responses. Problems arise when one or other arm of the immune system develops inappropriately, resulting in inappropriate effector responses to harmless food proteins (allergy) or inadequate responses to pathogens (disease susceptibility).

Transplantation of hNT neurons into the ischemic cortex: Cell survival and effect on sensorimotor behavior

Cell transplantation offers a potential new treatment for stroke. Animal studies using models that produce ischemic damage in both the striatum and the frontal cortex have shown beneficial effects when hNT cells (postmitotic immature neurons) were transplanted into the ischemic striatum. In this study, we investigated the effect of hNT cells in a model of stroke in which the striatum remains intact and damage is restricted to the cortex. hNT cells were transplanted into the ischemic cortex 1 week after stroke induced by distal middle cerebral artery occlusion (dMCAo). The cells exhibited robust survival at 4 weeks posttransplant even at the lesion border. hNT cells did not migrate, but they did extend long neurites into the surrounding parenchyma mainly through the white matter. Neurite extension was predominantly toward the lesion in ischemic animals but was bidirectional in uninjured animals. Extension of neurites through the cortex toward the lesion was also seen when there was some surviving cortical tissue between the graft and the infarct. Prolonged deficits were obtained in four tests of sensory-motor function. hNT-transplanted animals showed a significant improvement in functional recovery on one motor test, but there was no effect on the other three tests relative to control animals. Thus, despite clear evidence of graft survival and neurite extension, the functional benefit of hNT cells after ischemia is not guaranteed. Functional benefit could depend on other variables, such as infarct location, whether the cells mature, the behavioral tests employed, rehabilitation training, or as yet unidentified factors.

The influence of environment on development of the mucosal immune system

The mucosal immune system expresses active responses against pathogens and also tolerance against harmless food and commensal bacterial antigens. The mechanisms that determine which of these outcomes occur after recognition of antigens by T-cells are not clear. One possibility is that it is determined by the initial interaction between a dendritic and a naïve T-cell in organised lymphoid tissue. However, such organised structures are, evolutionarily, quite recent and the original immune system must have made appropriate responses in more diffuse immunological architecture; a second possibility is that the critical interaction is between primed T-cells and their environment, in the lamina propria of the intestine. The mucosal immune system of neonates is poorly developed and inefficient at expressing appropriate immune responses. Development is influenced by a range of environmental factors including maternally derived antigen or antibody and commensal flora and pathogens. The intestine is a complex immunological structure in which the immune system and the macro- and microenvironment interact.

The cytotoxicity and mode of action of 2,3,4-trisubstituted pyrroles and related derivatives in human Tmolt4 leukemia cells

4-Carbethoxy-1-methyl-2-phenacyl-3-phenylpyrrole (9), 4-carbethoxy-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)pyrrole (10) and 2-(4-methoxybenzoyl)-3,4-bis-(4-methoxyphenyl)pyrrole (11) proved to be potent cytotoxic agents against the growth of murine and human leukemias and lymphomas. Selective toxicity was demonstrated against the growth of solid tumors, e.g., human adenocarcinoma of the colon SW480 and ileum HCT-8, glioma U-87-MG, and rat UMR-106 osteosarcoma. A mode of action study in Tmolt4 leukemia cells demonstrated that the agents inhibited de novo purine synthesis at the regulatory sites PRPP-amido transferase, IMP dehydrogenase as well as dihydrofolate reductase resulting in significant inhibition of DNA synthesis in 60 min. Other biochemical sites which were affected significantly were thymidylate synthetase, DNA polymerase alpha, RNA polymerases, nucleoside kinase and ribonucleoside reductase.

Antagonist activities of mecamylamine and nicotine show reciprocal dependence on beta subunit sequence in the second transmembrane domain

We show that a portion of the TM2 domain regulates the sensitivity of beta subunit-containing rat neuronal nicotinic AChR to the ganglionic blocker mecamylamine, such that the substitution of 4 amino acids of the muscle beta subunit sequence into the neuronal beta4 sequence decreases the potency of mecamylamine by a factor of 200 and eliminates any long-term effects of this drug on receptor function. The same exchange of sequence that decreases inhibition by mecamylamine produces a comparable potentiation of long-term inhibition by nicotine. Inhibition by mecamylamine is voltage-dependent, suggesting a direct interaction of mecamylamine with sequence elements within the membrane field. We have previously shown that sensitivity to TMP (tetramethylpiperidine) inhibitors is controlled by the same sequence elements that determine mecamylamine sensitivity. However, inhibition by bis-TMP compounds is independent of voltage. Our experiments did not show any influence of voltage on the inhibition of chimeric receptors by nicotine, suggesting that the inhibitory effects of nicotine are mediated by binding to a site outside the membrane's electric field. An analysis of point mutations indicates that the residues at the 6' position within the beta subunit TM2 domain may be important for determining the effects of both mecamylamine and nicotine in a reciprocal manner. Single mutations at the 10' position are not sufficient to produce effects, but 6' 10' double mutants show more effect than do the 6' single mutants.

Health services reform and human resource management in Hong Kong public hospitals

This article discusses the empirical study of reform in the human resource management function in the Hong Kong Hospital Authority. It describes the prior management of the hospitals based on the civil service administration model before looking at management reform in general. From this research, the creative tensions between the centrifugal and centripetal forces in the pursuit of 'effectiveness', 'efficiency' and 'economy' are explored in terms of decentralization. A survey of line managers, in eleven Hospital Authority hospitals, revealed the progress of decentralization: a majority of respondents felt that, over the previous five years, managers at their level had been given greater responsibility for human resource management issues. In spite of the widespread perception of increased decentralization, however, it was recognized that there are limits to decentralization. It was the routine administration rather than the policy formulation and interpretation which had been decentralized, and hospitals continued to rely on the Hospital Authority Head of Office for guidance on policy interpretation. Several barriers to the effective decentralization of responsibility for human resource management were identified, including a lack of management skill, knowledge and time, the attitudes of some managers and the tight control of budget.

Activation of T cells from the intestinal lamina propria of the pig

This study found CD4+ T cells present in leucocyte populations isolated from the lamina propria of the pig to be almost exclusively CD45RC-, consistent with their being highly differentiated by exposure to antigen. Following activation in vitro these cells up-regulated expression of IL-2R with similar kinetics to splenic CD4+ cells. However, while splenic cells progressively secreted IL-2 into cultures during the first 24 h, IL-2 was not detected in supernatants of lamina propria cells after 8 h. Reverse-transcriptase polymerase chain reaction (RT-PCR) confirmed that this reflected a transcriptional difference: IL-2 transcripts were detected in cultures of splenic and lamina propria cells in the first few hours after activation but persisted only in splenic cells. In contrast, IL-4 transcripts were strongly expressed by activated lamina propria cells. Cell-cycle analysis demonstrated that fewer lamina propria CD4+ cells progressed into S-phase than did splenic CD4+ cells (26.0 11.1% and 45.0 11.3% respectively, P=0.011). Our results suggest that CD4+ T cells in these populations are differentiated effector cells whose potential for expansion may be dependent upon local factors. Such cells may be targets for immunoregulation by their local microenvironment.

Analysis of the immunological cross reactivities of 213 well characterized monoclonal antibodies with specificities against various leucocyte surface antigens of human and 11 animal species

213 Monoclonal antibodies (mAbs) raised against leucocyte surface antigens from human and 11 animal species were analyzed for reactivities against leucocytes from human and 15 different animal species. We found 77 mAbs (36%) to cross-react. Altogether, 217 cross reactions were registered out of 3195 possible combinations (7%). Most of the cross reacting mAbs had integrin or MHC class II specificities. This study defined cross reactions on the following markers: CD1a, 1c, 2, 4, 5, 8, 9, 11a, 11b, 14, 18, 20, 21, 23, 29, 31, 41, 43, 44, 45, 45R, 46, 49, 61, 62L, TCR gamma/delta, BCR, Thy-1, MHC class I and MHC class II, Swine-WC7 and Cattle-WC1. In order to characterize the molecular weight (MW) of the corresponding cross reacting antigens, selected mAbs were used to immunoprecipitate the antigens. The MW's of the analyzed precipitated antigens were in good agreement with the MWs of the homologous antigens. The followed strategy was found to be efficient and economical in defining new leucocyte antigen reactive mAbs.

Summary of the first round analyses of the Second International Swine CD Workshop

The reactivity of 176 monoclonal antibodies (mAb) submitted to the Second International Swine CD Workshop, together with 19 internal standards, was analyzed by flow cytometry on 16 different cell types as a means of establishing the proper cell subset for later detailed clustering analyses. The exact CD subset reactivity of the 19 internal standard mAb had been characterized in the First International Swine CD Workshop. The flow cytometric analyses resulted in 40 data sets which were then subjected to statistical clustering using the Leukocyte Typing Database IV (LTDB4) software. As result of this work, 22 clusters were defined. After review of these results, panels of mAb from the defined first round clusters were assigned to cell subsets. The respective mAb in those first round clusters were then distributed to subset group researchers for further examination during the second round of the workshop.

Developing an integrated public health information system for Missouri

The Missouri Department of Health realized it had a problem with 67 different information systems that ran on different platforms and could not communicate with one another. A new, integrated information system, the Missouri Health Strategic Architectures and Information Cooperative (MOHSAIC) is being developed based on information engineering (IE). This article describes IE, the process of developing MOHSAIC, and some key lessons learned in developing the system. Some of the lessons learned include the importance of executive sponsorship, tension between efficiency and program accountability, importance of confidentiality, and difficulties of funding an integrated system. The article stresses how integrated information systems will be important for the viability of public health under health care reform.

Comparison of the requirement of porcine peripheral blood monocytes and intestinal lamina propria macrophages as accessory cells in primary allogeneic mixed leukocyte responses and oxidative mitogenesis

Differences and/or similarities of the accessory cell activity of circulating peripheral blood monocytes (PBM) and intestinal lamina propria macrophages (LPM) in the pig have never been evaluated. Therefore this study was designed to compare the accessory cell activity of these cells in the induction of primary allogeneic mixed leukocyte responses (MLR) and polyclonal mitogenesis. Splenic adherent cells (SPAC) were used as control accessory cells. It was observed that PBM, LPM and SPAC induced significant T cell proliferation in response to allo-antigens. Significantly higher responses were elicited by SPAC, followed by PBM whereas, LPM induced low responses when cultures were established a T cell: accessory cell ratio of 1:1. PBM was the only accessory cell which induced significant responses at a cell ratio of 10:1. Whereas LPM and SPAC were able to induce significant oxidative mitogenesis, PBM were poor stimulators of this response. The observed difference between PBM, SPAC and LPM is attributed partly to differences in number of major histocompatibility complex (MHC) class II positive cells and the intensity of expression of the glycoproteins.

The accessory cell activity of porcine intestinal macrophages in the induction of T cell responses

Although intestinal macrophages stimulated significant T cell responses to MHC class II antigens and polyclonalmitogens, they were weak stimulators of ovalbumin-driven responses. These cells showed numerous and large endocytic vacuoles, lysosomes and phagolysosomes which may be indicative of active phagocytosis during the isolation process. The poor antigen presenting activity of the cells in protein antigen-elicited may be an in vitro artifact attributed to acquired inefficiency in antigen uptake and/or processing.

The delayed-emesis syndrome from cisplatin: phase III evaluation of ondansetron versus placebo

Cisplatin may evoke both an acute emetic response during the first 24 hours following treatment and a less well-recognized syndrome of delayed emesis. While delayed emesis is usually less severe in terms of frequency of vomiting episodes, the problem continues to result in significant morbidity. In comparison with acute emesis, the exact pathogenesis of the delayed emesis syndrome remains unclear. Although a combination of oral metoclopramide and dexamethasone is effective in many patients in preventing delayed emesis, almost 50% continue to experience at least one emetic episode when treated with this regimen. A phase III multicenter study has evaluated oral ondansetron versus placebo in the prevention of the delayed-emesis syndrome in 50 patients during days 2 through 5 following high-dose cisplatin administration. Although the daily rates of complete emetic control, failure, and control of nausea favor ondansetron, this trial is statistically inconclusive in establishing efficacy of ondansetron as a single agent in the prevention of delayed emesis. Ondansetron was well tolerated in the dose and schedule used.

Modulation of monocyte Mo2 surface antigen expression by exposure to respiratory syncytial virus

The Mo2 antibody recognizes a monocyte-specific cell surface antigen of unknown function. Upward modulation of Mo2 surface epitope density was demonstrated in response to 72-hr culture of monocytes with respiratory syncytial virus (RSV), but this was not seen after culture with phytohemagglutinin or other respiratory viruses. Monoclonal antibody probes for RSV proteins were used to demonstrate probable replication of RSV proteins in peripheral blood monocytes and pulmonary alveolar macrophages. These data provide possible clues to the biologic role of the Mo2 antigen.