The empty pelvis syndrome: a core data set from the PelvEx collaborative

BACKGROUND

Empty pelvis syndrome (EPS) is a significant source of morbidity following pelvic exenteration (PE), but is undefined. EPS outcome reporting and descriptors of radicality of PE are inconsistent; therefore, the best approaches for prevention are unknown. To facilitate future research into EPS, the aim of this study is to define a measurable core outcome set, core descriptor set and written definition for EPS. Consensus on strategies to mitigate EPS was also explored.

METHOD

Three-stage consensus methodology was used: longlisting with systematic review, healthcare professional event, patient engagement, and Delphi-piloting; shortlisting with two rounds of modified Delphi; and a confirmatory stage using a modified nominal group technique. This included a selection of measurement instruments, and iterative generation of a written EPS definition.

RESULTS

One hundred and three and 119 participants took part in the modified Delphi and consensus meetings, respectively. This encompassed international patient and healthcare professional representation with multidisciplinary input. Seventy statements were longlisted, seven core outcomes (bowel obstruction, enteroperineal fistula, chronic perineal sinus, infected pelvic collection, bowel obstruction, morbidity from reconstruction, re-intervention, and quality of life), and four core descriptors (magnitude of surgery, radiotherapy-induced damage, methods of reconstruction, and changes in volume of pelvic dead space) reached consensus-where applicable, measurement of these outcomes and descriptors was defined. A written definition for EPS was agreed.

CONCLUSIONS

EPS is an area of unmet research and clinical need. This study provides an agreed definition and core data set for EPS to facilitate further research.

Student selection in radiography education. A narrative review

OBJECTIVES

Due to effects on study success, radiography student selection has a major impact on higher education institutions and applicants. However, there is very little research to demonstrate which selection methods and contents are most successful in radiography education. This study aimed to describe the methods and contents used in radiography student selection and factors related to study success.

KEY FINDINGS

A narrative review was undertaken. A computerized search in four databases limited to studies published between January 2000 and June 2021. Ten quantitative, mainly retrospective, studies were included. The review identified 23 selection methods; of these, interview (n = 4), Scholastic Aptitude Test (n = 3), American College Test (n = 2) and reference letter (n = 2) were used more than once in radiography student selection. The content of the selection methods was identified in four categories including 44 factors. The most often assessed content was category of learning skills while the least often assessed concerned categories of social skills, personality traits and career choice. Regarding study success, factors of learning skills, namely mathematics, physics, biology, anatomy, physiology, natural sciences, a composite of factors comprising electronics and a composite of factors comprising mechanics predicted study success. Factors of social skills, personality traits and career choice were not related to study success.

CONCLUSION

The methods used and contents assessed vary greatly in radiography student selection. The results suggest using the content in the four categories in the selection of radiography students.

IMPLICATIONS FOR PRACTICE

Further research is needed to clarify the methods, with knowledge of the reliability and validity and the contents for the suggested categories, and to demonstrate their relationship to study success and identify the core content of radiography student selection especially in European context.

Transcriptome analysis of non human primate-induced pluripotent stem cell-derived cardiomyocytes in 2D monolayer culture vs. 3D engineered heart tissue

AIMS

Stem cell therapy has shown promise for treating myocardial infarction via re-muscularization and paracrine signalling in both small and large animals. Non-human primates (NHPs), such as rhesus macaques (Macaca mulatta), are primarily utilized in preclinical trials due to their similarity to humans, both genetically and physiologically. Currently, induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) are delivered into the infarcted myocardium by either direct cell injection or an engineered tissue patch. Although both approaches have advantages in terms of sample preparation, cell-host interaction, and engraftment, how the iPSC-CMs respond to ischaemic conditions in the infarcted heart under these two different delivery approaches remains unclear. Here, we aim to gain a better understanding of the effects of hypoxia on iPSC-CMs at the transcriptome level.

METHODS AND RESULTS

NHP iPSC-CMs in both monolayer culture (2D) and engineered heart tissue (EHT) (3D) format were exposed to hypoxic conditions to serve as surrogates of direct cell injection and tissue implantation in vivo, respectively. Outcomes were compared at the transcriptome level. We found the 3D EHT model was more sensitive to ischaemic conditions and similar to the native in vivo myocardium in terms of cell-extracellular matrix/cell-cell interactions, energy metabolism, and paracrine signalling.

CONCLUSION

By exposing NHP iPSC-CMs to different culture conditions, transcriptome profiling improves our understanding of the mechanism of ischaemic injury.

Comparison of Non-human Primate versus Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Treatment of Myocardial Infarction

Non-human primates (NHPs) can serve as a human-like model to study cell therapy using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). However, whether the efficacy of NHP and human iPSC-CMs is mechanistically similar remains unknown. To examine this, RNU rats received intramyocardial injection of 1 × 107 NHP or human iPSC-CMs or the same number of respective fibroblasts or PBS control (n = 9-14/group) at 4 days after 60-min coronary artery occlusion-reperfusion. Cardiac function and left ventricular remodeling were similarly improved in both iPSC-CM-treated groups. To mimic the ischemic environment in the infarcted heart, both cultured NHP and human iPSC-CMs underwent 24-hr hypoxia in vitro. Both cells and media were collected, and similarities in transcriptomic as well as metabolomic profiles were noted between both groups. In conclusion, both NHP and human iPSC-CMs confer similar cardioprotection in a rodent myocardial infarction model through relatively similar mechanisms via promotion of cell survival, angiogenesis, and inhibition of hypertrophy and fibrosis.

High-throughput screening of tyrosine kinase inhibitor cardiotoxicity with human induced pluripotent stem cells

Tyrosine kinase inhibitors (TKIs), despite their efficacy as anticancer therapeutics, are associated with cardiovascular side effects ranging from induced arrhythmias to heart failure. We used human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), generated from 11 healthy individuals and 2 patients receiving cancer treatment, to screen U.S. Food and Drug Administration-approved TKIs for cardiotoxicities by measuring alterations in cardiomyocyte viability, contractility, electrophysiology, calcium handling, and signaling. With these data, we generated a "cardiac safety index" to reflect the cardiotoxicities of existing TKIs. TKIs with low cardiac safety indices exhibit cardiotoxicity in patients. We also derived endothelial cells (hiPSC-ECs) and cardiac fibroblasts (hiPSC-CFs) to examine cell type-specific cardiotoxicities. Using high-throughput screening, we determined that vascular endothelial growth factor receptor 2 (VEGFR2)/platelet-derived growth factor receptor (PDGFR)-inhibiting TKIs caused cardiotoxicity in hiPSC-CMs, hiPSC-ECs, and hiPSC-CFs. With phosphoprotein analysis, we determined that VEGFR2/PDGFR-inhibiting TKIs led to a compensatory increase in cardioprotective insulin and insulin-like growth factor (IGF) signaling in hiPSC-CMs. Up-regulating cardioprotective signaling with exogenous insulin or IGF1 improved hiPSC-CM viability during cotreatment with cardiotoxic VEGFR2/PDGFR-inhibiting TKIs. Thus, hiPSC-CMs can be used to screen for cardiovascular toxicities associated with anticancer TKIs, and the results correlate with clinical phenotypes. This approach provides unexpected insights, as illustrated by our finding that toxicity can be alleviated via cardioprotective insulin/IGF signaling.

Chemically Defined Culture and Cardiomyocyte Differentiation of Human Pluripotent Stem Cells

Since the first discovery that human pluripotent stem cells (hPS cells) can differentiate to cardiomyocytes, efforts have been made to optimize the conditions under which this process occurs. One of the most effective methodologies to optimize this process is reductionist simplification of the medium formula, which eliminates complex animal-derived components to help reveal the precise underlying mechanisms. Here we describe our latest, cost-effective and efficient methodology for the culture of hPS cells in the pluripotent state using a modified variant of chemically defined E8 medium. We provide exact guidelines for cell handling under these conditions, including non-enzymatic EDTA passaging, which have been optimized for subsequent cardiomyocyte differentiation. We describe in depth the latest version of our monolayer chemically defined small molecule differentiation protocol, including metabolic selection-based cardiomyocyte purification and the addition of triiodothyronine to enhance cardiomyocyte maturation. Finally, we describe a method for the dissociation of hPS cell-derived cardiomyocytes, cryopreservation, and thawing.

Frequent mild cognitive deficits in several functional domains in elderly patients with heart failure without known cognitive disorders

BACKGROUND

The objective of the present study was to investigate whether mild cognitive deficits are present in patients with heart failure (HF) despite absence of any known cognitive disorder.

METHODS AND RESULTS

A well defined group of patients (n = 40) with heart failure completed a cognitive screening check list, a depression screening questionnaire, and a battery consisting of neuropsychological tests assessing 5 different cognitive domains: speed/attention, episodic memory, visuospatial functions, language, and executive functions. The neuropsychological results were compared with those from a group of healthy control subjects (n = 41). The patients with HF displayed cognitive impairment compared with the control group within the domains speed and attention, episodic memory, visuospatial functions, and language. Among them, 34 HF patients (85%) could be classified with mild cognitive impairment (MCI), the majority as nonamnestic MCI, ie, with no memory impairment.

CONCLUSIONS

Considering the high occurrence of mild cognitive deficits among HF patients without known cognitive disorders, closer attention should be paid to their self-care and compliance. Inadequate self-care and compliance could lead to more frequent hospitalizations. Furthermore, the HF patients may be at increased risk of dementia.

Assessment of a multi-marker risk score for predicting cause-specific mortality at three years in older patients with heart failure and reduced ejection fraction

BACKGROUND

Due to increasing co-morbidity associated with aging, heart failure (HF) has become more prevalent and heterogeneous in older individuals, and non-cardiovascular (CV) mortality has increased. Previously, we defined a multi-marker modality that included cystatin C (CysC), troponin T (TnT), and age. Here, we validated this multi-marker risk score by evaluating its predictions of all-cause mortality and CV mortality in an independent population of older individuals with HF and reduced ejection fraction (HFrEF).

METHODS

This prospective cohort study included 124 patients, median age 73 years, that had HFrEF. We determined all-cause mortality and CV mortality at a 3-year follow-up. We compared the risk score to the N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) for predicting all-cause mortality and CV mortality.

RESULTS

High risk scores were associated with both all-cause mortality (HR 4.2, 95% CI 2.2-8.1, p < 0.001) and CV mortality (HR 3.6, 95% CI 1.7-8.0, p = 0.0015). Receiver operating characteristics showed similar efficacy for the risk score and NT-proBNP in predicting all-cause mortality (HR 0.74, 95% CI 0.65-0.81 vs. HR 0.74, 95% CI 0.65-0.81, p = 0.99) and CV mortality (HR 0.68, 95% CI 0.59-0.76 vs. HR 0.67, 95% CI 0.58-0.75, p = 0.95). When the risk score was added to the NT-proBNP, the continuous net reclassification improvement was 56% for predicting all-cause mortality (95% CI 18-95%, p = 0.004) and 45% for predicting CV mortality (95% CI 2-89%, p = 0.040).

CONCLUSIONS

In HFrEF, a risk score that included age, TnT, and CysC showed efficacy similar to the NT-proBNP for predicting all-cause mortality and CV mortality in an older population.

Heart dysfunction in patients with acute ischemic stroke or TIA does not predict all-cause mortality at long-term follow-up

BACKGROUND

Despite heart failure being a substantial risk factor for stroke, few studies have evaluated the predictive value of heart dysfunction for all-cause mortality in patients with acute ischemic stroke, in particular in the elderly. The aim of this study was to investigate whether impaired heart function in elderly patients can predict all-cause mortality after acute ischemic stroke or transient ischemic attack (TIA).

METHODS

A prospective long-term follow-up analysis was performed on a hospital cohort consisting of n = 132 patients with mean age 73 ± 9 years, presenting with acute ischemic stroke or transient ischemic attack, without atrial fibrillation. All patients were examined by echocardiography during the hospital stay. Data about all-cause mortality were collected at the end of the follow-up period. The mean follow-up period was 56 ± 22 months.

RESULTS

In this cohort, 58% of patients with acute ischemic stroke or TIA had heart dysfunction. Survival analysis showed that heart dysfunction did not predict all-cause mortality in this cohort. Furthermore, in multivariate regression analysis age (HR 5.401, Cl 1.97-14.78, p < 0.01), smoking (HR 3.181, Cl 1.36-7.47, p < 0.01), myocardial infarction (HR 2.826, Cl 1.17-6.83, p < 0.05) were independent predictors of all-cause mortality.

CONCLUSION

In this population with acute ischemic stroke or TIA and without non-valvular atrial fibrillation, impaired heart function does not seem to be a significant predictor of all-cause mortality at long-term follow-up.

Red blood cell distribution width and its relation to cardiac function and biomarkers in a prospective hospital cohort referred for echocardiography

BACKGROUND

Red blood cell distribution width (RDW), a measure of anisocytosis, is a prognostic biomarker for heart failure (HF). However it is still unclear how RDW is associated with heart function and established cardiac biomarkers.

METHODS AND RESULTS

In a prospective hospital cohort of 296 patients referred for echocardiography because of suspected HF, blood sampling and clinical examination were performed within 24h after echocardiography. The patients were divided into four HF groups, including one group where the HF diagnosis was uncertain (gray zone). In the patients the mean age was 70 ± 11 years, 44% with systolic HF (SHF), 18% with heart failure with normal ejection fraction (HFNEF), 17% with gray zone and 21% without HF (non-HF). RDW was higher among patients with SHF and HFNEF, compared with gray zone and non-HF patients. The distribution of different variables over the RDW quartiles showed an inverse correlation between RDW levels and LVEF and a positive correlation between RDW and NT-proBNP levels. Further analysis with stepwise multiple linear regression demonstrated that NT-proBNP levels, but not LVEF, were independently correlated with RDW.

CONCLUSION

In patients referred for echocardiography because of suspected HF, RDW levels were higher in patients with SHF and HFNEF. Moreover, NT-proBNP levels were independently linked with elevated RDW.

Increased comorbidities in heart failure patients ≥ 85 years but declined from >90 years: data from the Swedish Heart Failure Registry

OBJECTIVES

Epidemiological studies of elderly heart failure (HF) patients (≥ 85 years) are limited with inconsistent findings. Our objective is to confirm and extend epidemiological study in elderly (≥ 85 years) patients using the Swedish Heart Failure Registry database.

METHODS

This retrospective study included 8,347 HF patients aged ≤ 65 years and 15,889 HF patients aged ≥ 85 years. Elderly population was further divided into two subgroups: 11,412 patients were 85-90 years and 4,477 patients were >90 years.

RESULTS

The ≥ 85 year group was characterized by more women, higher systolic blood pressure (SBP), lower body-mass index (BMI), more than twice as many HF with normal left ventricular ejection fraction (HFNEF), higher incidence of cardiovascular and non-cardiovascular comorbidities and less use of proven therapeutics compared with the ≤ 65 year group. Compared with the 85-90 year subgroup, the > 90 year subgroup had a decline in cardiovascular and non-cardiovascular comorbidities except renal insufficiency and anaemia which continued to increase with ageing (p<0.01). Tendency was the same regardless of gender but slightly different between systolic HF (SHF) and HFNEF. In the group with HFNEF, there were more women, higher SBP, lower N-terminal pro-B-type natriuretic peptide levels, less ischaemic heart disease, more hypertension and left bundle branch block regardless of age. Atrial fibrillation was more frequent in patients with HFNEF than with SHF in the elderly group (p<0.01). Patients with HFNEF in the > 90 year subgroup had increasing incidence of ischaemic heart disease compared to 85-90 year group (p<0.01).

CONCLUSIONS

HF patients ≥ 85 years had increased cardiovascular and non-cardiovascular comorbidities but with a decline from >90 years.

Theft reduction in a grocery store through product identification and graphing of losses for employees

Shoplifting and employee theft constitute a major problem for retailers. Previous research has described techniques for effectively reducing either type of theft but has not addressed the problem of thefts of unspecified origin. In a grocery store we evaluated the effect of identifying for employees frequently stolen products from three groups of items and graphing, twice weekly in the lunchroom, losses for the separate groups. After the products were identified and losses graphed, thefts from the three groups dropped from eight per day to two per day.

Desflurane induces more cerebral vasodilation than isoflurane at the same A-line autoregressive index level

BACKGROUND

Clinical use of desflurane in neuroanesthesia remains under debate. Comparison of dose-dependent vasodilatory properties between desflurane and isoflurane, the more traditional volatile agent for clinical neuroanesthesia, requires equianesthetic dosing of the agents. Reproducible neurophysiological measurements of the level of anesthesia in an individual, e.g. the A-line autoregressive index (AAI), can be used for an equipotent dosage of two volatile agents in the same individual.

METHODS

Desflurane and isoflurane, in randomized order, were titrated to a stable AAI level of 15-20 in 18 ASA I or II patients. The mean flow velocity (Vmca) and pulsatility index (PI) in the middle cerebral artery were then measured with transcranial Doppler at an end-tidal CO(2) concentration of 4.4%.

RESULTS

For desflurane Vmca was 11% higher [95% confidence interval (CI), 5-18%; P = 0.0020] and PI was 13% lower (95% CI, 3-23%; P = 0.0083) than for isoflurane. The mean arterial blood pressure did not differ between the agents. The fraction of MAC necessary for the intended AAI level was 35% lower (95% CI, 20-49%; P = 0.00016) with desflurane than with isoflurane.

CONCLUSION

Desflurane was associated with more cerebral vasodilation than isoflurane at the same depth of anesthesia, as indicated by the AAI. This attributes further reason for caution in the use of desflurane in clinical neuroanesthesia. The difference between desflurane and isoflurane in the MAC fractions required for the same AAI level confirms the limitations of MAC in defining the level of anesthesia.

Sevoflurane induces less cerebral vasodilation than isoflurane at the same A-line autoregressive index level

BACKGROUND

The use of sevoflurane in neuroanesthesia is still under debate. Comparison of dose-dependent vasodilatory properties between sevoflurane and isoflurane, the more traditional neuroanesthetic agent, requires comparable dosing of the agents. A-line autoregressive index (AAI) provides reproducible individual measurement of anesthetic depth.

METHODS

Sevoflurane and isoflurane, in randomized order, were titrated to a stable AAI of 15-20 in each of 18 ASA I or II patients. The mean flow velocity (Vmca) and pulsatility index (PI) in the middle cerebral artery were measured with transcranial Doppler at an end-tidal CO2 of 4.5%.

RESULTS

For sevoflurane Vmca was 18% lower [95% confidence interval (CI) 12-22%; P < 0.00001] and PI was 23% higher (95% CI 12-33%; P = 0.0013) than for isoflurane. Mean arterial blood pressure did not differ between the two agents. The minimum alveolar concentration (MAC) fraction necessary to reach the intended AAI level was 13% higher (95% CI 5-20%; P = 0.0079) with sevoflurane than with isoflurane.

CONCLUSION

Sevoflurane induced less cerebral vasodilation than isoflurane at the same depth of anesthesia, measured by AAI, and hence seems more favorable for clinical neuroanesthesia. In our opinion the difference between sevoflurane and isoflurane in the MAC fraction required to attain the same AAI level demonstrates the limitations of MAC in defining the level of anesthesia.

Desflurane results in higher cerebral blood flow than sevoflurane or isoflurane at hypocapnia in pigs

BACKGROUND

In clinical neuroanaesthesia, the increase in cerebral blood flow (CBF) and intracranial pressure caused by the cerebral vasodilative effects of an inhalational anaesthetic agent is counteracted by the cerebral vasoconstriction induced by hypocapnia. Desflurane and sevoflurane may have advantages over the more traditionally used isoflurane in neuroanaesthesia but their dose-dependent vasodilative effects at hypocapnia have not been compared in the same model using truly equipotent minimal alveolar concentrations (MACs).

METHOD

Desflurane, sevoflurane and isoflurane were administered in a randomized order to six pigs at 0.5 and 1.0 MAC. The intra-arterial xenon clearance technique was used to calculate CBF. Blood pressure was invasively monitored. Cerebral and systemic physiological variables were recorded first at normocapnia (PaCO2 5.6 kPa) and then at hypocapnia (PaCO2 3.5 kPa). Electroencephalographic (EEG) activity was continuously recorded.

RESULTS

None of the three agents abolished cerebrovascular reactivity to hyperventilation, and at 0.5 MAC all had similar effects on CBF at hypocapnia. Desflurane at 1.0 MAC was associated with 16% higher CBF (P = 0.027) at hypocapnia than isoflurane, and with 24% higher CBF (P = 0.020) than sevoflurane. There was no seizure activity in the EEG.

CONCLUSION

More cerebral vasodilation at hypocapnia with high doses of desflurane than with sevoflurane or isoflurane indicates that desflurane might be less suitable for neuroanaesthesia than sevoflurane and isoflurane.

Cerebral blood flow at 0.5 and 1.0 minimal alveolar concentrations of desflurane or sevoflurane compared with isoflurane in normoventilated pigs

Whether desflurane and sevoflurane have clinical advantages over isoflurane in neuroanesthesia is much debated. A porcine model was used for comparison of desflurane and sevoflurane with isoflurane with respect to their cerebrovascular effects. The minimal alveolar concentration (MAC) of each of the three agents was first determined in a standardized manner in six domestic juvenile pigs to enhance comparison reliability. Six other pigs were then anesthetized with isoflurane, desflurane, and sevoflurane, given in sequence to each pig in an even crosswise order with the first agent also used to maintain anesthesia during surgical preparation. Cerebral blood flow (CBF) was calculated from the clearance curve of intraarterially injected 133Xe. The mean arterial pressure (MAP) was invasively monitored. The estimated cerebrovascular resistance (CVRe) was calculated by dividing MAP with CBF, thereby approximating the cerebral perfusion pressure with MAP. For both MAC levels, the trend for CBF was desflurane > isoflurane > sevoflurane, and the trend for MAP and CVRe was sevoflurane > isoflurane > desflurane. Statistical comparison of desflurane and sevoflurane with isoflurane with respect to CBF and MAP revealed two statistically significant differences-namely, that CBF at 1.0 MAC desflurane was 17% higher than CBF at 1.0 MAC isoflurane (P =.0025) and that MAP at 1.0 MAC sevoflurane was 16% higher than MAP at 1.0 MAC isoflurane (P =.011). Consequently, in this study at normocapnia, these agents did not seem to differ much in their cerebral vasodilating effects at lower doses. At higher doses, however, desflurane, in contrast to sevoflurane, was found to induce more cerebral vasodilation than isoflurane.

PCR-generated linear DNA fragments utilized as a hantavirus DNA vaccine

The field of DNA vaccines has grown rapidly, and since most such vaccines involve the inoculation of large circular DNA molecules previously propagated in bacteria, several inconveniences (e.g. the presence of antibiotic resistance genes, impurities from bacterial cultures or inefficient uptake of the large and bulky plasmid DNA molecules to the nucleus) are debated. In this study, we have explored the possibility of using smaller and more flexible PCR-generated linear DNA fragments instead. Phosphorothioate (PTO)-modified primers were used successfully to protect the PCR-generated DNA fragments from exonuclease degradation, and by using a nuclear localization signal-peptide to target the linear DNA to the nucleus the immune response against the encoded antigen was further improved. This approach was tested in cell culture using a sensitive reporter system and in vivo with DNA encoding the amino-terminus of the Puumala hantavirus nucleocapsid protein. Our results indicate that linear DNA fragments have a great potential as a genetic vaccine and phosphorothioate modification in combination with a nuclear localization signal peptide increase the stability and targets the linear DNA molecules to the nucleus resulting in an improved biological response examined both in vitro and in vivo.

Kinesin-dependent movement on microtubules precedes actin-based motility of vaccinia virus

Vaccinia virus, a close relative of the causative agent of smallpox, exploits actin polymerization to enhance its cell-to-cell spread. We show that actin-based motility of vaccinia is initiated only at the plasma membrane and remains associated with it. There must therefore be another form of cytoplasmic viral transport, from the cell centre, where the virus replicates, to the periphery. Video analysis reveals that GFP-labelled intracellular enveloped virus particles (IEVs) move from their perinuclear site of assembly to the plasma membrane on microtubules. We show that the viral membrane protein A36R, which is essential for actin-based motility of vaccinia, is also involved in microtubule-mediated movement of IEVs. We further show that conventional kinesin is recruited to IEVs via the light chain TPR repeats and is required for microtubule-based motility of the virus. Vaccinia thus sequentially exploits the microtubule and actin cytoskeletons to enhance its cell-to-cell spread.

LcrV is a channel size-determining component of the Yop effector translocon of Yersinia

Delivery of Yop effector proteins by pathogenic Yersinia across the eukaryotic cell membrane requires LcrV, YopB and YopD. These proteins were also required for channel formation in infected erythrocytes and, using different osmolytes, the contact-dependent haemolysis assay was used to study channel size. Channels associated with LcrV were around 3 nm, whereas the homologous PcrV protein of Pseudomonas aeruginosa induced channels of around 2 nm in diameter. In lipid bilayer membranes, purified LcrV and PcrV induced a stepwise conductance increase of 3 nS and 1 nS, respectively, in 1 M KCl. The regions important for channel size were localized to amino acids 127-195 of LcrV and to amino acids 106-173 of PcrV. The size of the channel correlated with the ability to translocate Yop effectors into host cells. We suggest that LcrV is a size-determining structural component of the Yop translocon.

Apically exposed, tight junction-associated beta1-integrins allow binding and YopE-mediated perturbation of epithelial barriers by wild-type Yersinia bacteria

Using polarized epithelial cells, primarily MDCK-1, we assessed the mode of binding and effects on epithelial cell structure and permeability of Yersinia pseudotuberculosis yadA-deficient mutants. Initially, all bacteria except the invasin-deficient (inv) mutant adhered apically to the tight junction areas. These contact points of adjacent cells displayed beta1-integrins together with tight junction-associated ZO-1 and occludin proteins. Indeed, beta1-integrin expression was maximal in the tight junction area and then gradually decreased along the basolateral membranes. Wild-type bacteria also opened gradually the tight junction to paracellular permeation of different-sized markers, viz., 20-, 40-, and 70-kDa dextrans and 45-kDa ovalbumin, as well as to their own translocation between adjacent cells in intimate contact with beta1-integrins. The effects on the epithelial cells and their barrier properties could primarily be attributed to expression of the Yersinia outer membrane protein YopE, as the yopE mutant bound but caused no cytotoxicity. Moreover, the apical structure of filamentous actin (F-actin) was disturbed and tight junction-associated proteins (ZO-1 and occludin) were dispersed along the basolateral membranes. It is concluded that the Yersinia bacteria attach to beta1-integrins at tight junctions. Via this localized injection of YopE, they perturb the F-actin structure and distribution of proteins forming and regulating tight junctions. Thereby they promote paracellular translocation of bacteria and soluble compounds.

The V-antigen of Yersinia is surface exposed before target cell contact and involved in virulence protein translocation

Type III-mediated translocation of Yop effectors is an essential virulence mechanism of pathogenic Yersinia. LcrV is the only protein secreted by the type III secretion system that induces protective immunity. LcrV also plays a significant role in the regulation of Yop expression and secretion. The role of LcrV in the virulence process has, however, remained elusive on account of its pleiotropic effects. Here, we show that anti-LcrV antibodies can block the delivery of Yop effectors into the target cell cytosol. This argues strongly for a critical role of LcrV in the Yop translocation process. Additional evidence supporting this role was obtained by genetic analysis. LcrV was found to be present on the bacterial surface before the establishment of bacteria target cell contact. These findings suggest that LcrV serves an important role in the initiation of the translocation process and provides one possible explanation for the mechanism of LcrV-induced protective immunity.

Yersinia outer proteins (YOPS) E, K and N are antigenic but non-protective compared to V antigen, in a murine model of bubonic plague

The pathogenic Yersiniae produce a range of virulence proteins, encoded by a 70 kb plasmid, which are essential for infection, and also form part of a contact-dependent virulence mechanism. One of these proteins, V antigen, has been shown to confer a high level of protection against parenteral infection with Y. pestis in murine models, and is considered to be a protective antigen. In this study, the protective efficacy of V antigen has been compared in the same model with that of other proteins (YopE, YopK and YopN), which are part of the contact-dependent virulence mechanism. Mice immunised with two intraperitoneal doses of V antigen or each of the Yops, administered with either Alhydrogel or interleukin-12, produced high antigen-specific serum IgG titres. As shown in previous studies, V+Alhydrogel was fully protective, and 5/5 mice survived a subcutaneous challenge with 90 or 9x10(3) LD50's of Y. pestis GB. In addition, these preliminary studies also showed that V+IL-12 was partially protective: 4/5 or 3/5 mice survived a challenge with 90 or 9x10(3) LD50's, respectively. In contrast, none of the mice immunised with the Yops survived the challenges, and there was no significant delay in the mean time to death compared to mice receiving a control protein. These results show that using two different vaccine regimens, Yops E, K and N, failed to elicit protective immune responses in a murine model of plague, whereas under the same conditions, V antigen was fully or partially protective.

Functional conservation of the effector protein translocators PopB/YopB and PopD/YopD of Pseudomonas aeruginosa and Yersinia pseudotuberculosis

Virulent Yersinia species cause systemic infections in rodents, and Y. pestis is highly pathogenic for humans. Pseudomonas aeruginosa, on the other hand, is an opportunistic pathogen, which normally infects only compromised individuals. Surprisingly, these pathogens both encode highly related contact-dependent secretion systems for the targeting of toxins into eukaryotic cells. In Yersinia, YopB and YopD direct the translocation of the secreted Yop effectors across the target cell membrane. In this study, we have analysed the function of the YopB and YopD homologues, PopB and PopD, encoded by P. aeruginosa. Expression of the pcrGVHpopBD operon in defined translocation-deficient mutants (yopB/yopD) of Yersinia resulted in complete complementation of the cell contact-dependent, YopE-induced cytotoxicity of Y. pseudotuberculosis on HeLa cells. We demonstrated that the complementation fully restored the ability of Y. pseudotuberculosis to translocate the effector molecules YopE and YopH into the HeLa cells. Similar to YopB, PopB induced a lytic effect on infected erythrocytes. The lytic activity induced by PopB could be prevented if the erythrocytes were infected in the presence of sugars larger than 3 nm in diameter, indicating that PopB induced a pore of similar size compared with that induced by YopB. Our findings show that the contact-dependent toxin-targeting mechanisms of Y. pseudotuberculosis and P. aeruginosa are conserved at the molecular level and that the translocator proteins are functionally interchangeable. Based on these similarities, we suggest that the translocation of toxins such as ExoS, ExoT and ExoU by P. aeruginosa across the eukaryotic cell membrane occurs via a pore induced by PopB.

YopK of Yersinia pseudotuberculosis controls translocation of Yop effectors across the eukaryotic cell membrane

Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins across the bacterial membranes is governed by closely related type III secretion systems. For pathogenic Yersinia, the protein transport across the eukaryotic cell membrane occurs by a polarized mechanism requiring two secreted proteins, YopB and YopD. YopB was recently shown to induce the formation of a pore in the eukaryotic cell membrane, and through this pore, translocation of Yop effectors is believed to occur (Håkansson et al., 1996b). We have previously shown that YopK of Yersinia pseudotuberculosis is required for the development of a systemic infection in mice. Here, we have analysed the role of YopK in the virulence process in more detail. A yopK-mutant strain was found to induce a more rapid YopE-mediated cytotoxic response in HeLa cells as well as in MDCK-1 cells compared to the wild-type strain. We found that this was the result of a cell-contact-dependent increase in translocation of YopE into HeLa cells. In contrast, overexpression of YopK resulted in impaired translocation. In addition, we found that YopK also influenced the YopB-dependent lytic effect on sheep erythrocytes as well as on HeLa cells. A yopK-mutant strain showed a higher lytic activity and the induced pore was larger compared to the corresponding wild-type strain, whereas a strain overexpressing YopK reduced the lytic activity and the apparent pore size was smaller. The secreted YopK protein was found not to be translocated but, similar to YopB, localized to cell-associated bacteria during infection of HeLa cells. Based on these results, we propose a model where YopK controls the translocation of Yop effectors into eukaryotic cells.

Fibreoptic laryngotracheoscopy via the laryngeal mask airway in children

BACKGROUND

Fibreoptic laryngotracheoscopy via the laryngeal mask airway-previously reported in adults but not in children-gives a better endoscopic view of the upper airway than does endoscopy via an endotracheal tube.

METHOD

The endoscopic procedure was carried out via a size 2 laryngeal mask in 4 spontaneously breathing children between 1 and 6 years old. Anaesthesia was induced and maintained with halothane in 50-100% oxygen.

RESULTS

The laryngeal mask was found to enable laryngotracheoscopy with a flexible 5.0-mm fibreoptic endoscope with no technical difficulties. Spontaneous ventilation could be readily preserved throughout the endoscopic procedure.

CONCLUSIONS

In children anaesthetized with halothane, flexible fibreoptic laryngotracheoscopy via a laryngeal mask is a useful method-offering technical advantages not achieved otherwise-provided that generally approved restrictions to the use of a laryngeal mask airway are taken into account.

Cell-surface-bound Yersinia translocate the protein tyrosine phosphatase YopH by a polarized mechanism into the target cell

YopH is translocated by cell-surface-bound bacteria through the plasma membrane to the cytosol of the HeLa cell. The transfer mechanism is contact dependent and polarizes the translocation to only occur at the contact zone between the bacterium and the target cell. More than 99% of the PTPase activity is associated with the HeLa cells. In contrast to the wild-type strain, the yopBD mutant cannot deliver YopH to the cytosol. Instead YopH is deposited in localized areas in the proximity of cell-associated bacteria. A yopN mutant secretes 40% of the total amount of YopH to the culture medium, suggesting a critical role of YopN in regulation of the polarized translocation. Evidence for a region in YopH important for its translocation through the plasma membrane of the target cell but not for secretion from the pathogen is provided.

Virulence plasmid-encoded YopK is essential for Yersinia pseudotuberculosis to cause systemic infection in mice

The virulence plasmid common to pathogenic Yersinia species encodes a number of secreted proteins denoted Yops (Yersinia outer proteins). Here, we identify and characterize a novel plasmid-encoded virulence determinant of Yersinia pseudotuberculosis, YopK. The yopK gene was found to be conserved among the three pathogenic Yersinia species and to be homologous to the previously described yopQ and yopK genes of Y. enterocolitica and Y. pestis, respectively. Similar to the other Yops, YopK expression and secretion were shown to be regulated by temperature and by the extracellular Ca2+ concentration; thus, yopK is part of the yop regulon. In addition, YopK secretion was mediated by the specific Yop secretion system. In Y. pseudotuberculosis, YopK was shown neither to have a role in this bacterium's ability to resist phagocytosis by macrophages nor to cause cytotoxicity in HeLa cells. YopK was, however, shown to be required for the bacterium to cause a systemic infection in both intraperitoneally and orally infected mice. Characterization of the infection kinetics showed that, similarly to the wild-type strain, the yopK mutant strain colonized and persisted in the Peyer's patches of orally infected mice. A yopE mutant which is impaired in cytotoxicity and in antiphagocytosis was, however, found to be rapidly cleared from these lymphoid organs. Neither the yopK nor the yopE mutant strain could overcome the primary host defense and reach the spleen. This finding implies that YopK acts at a different level during the infections process than the antiphagocytic YopE cytotoxin does.

Local skeletal muscle surface oxygen pressure fields after high-energy trauma

In the assessment of viability of traumatized muscle tissue clinical signs, including colour, consistency, capillary bleeding and contractility have been commonly used. One of these signs, discolouration, has been shown in earlier studies to be associated with impaired circulation and severe and irreversible changes of muscle electrolytes and energy metabolism. In this study the circulation and tissue oxygen pressure fields were studied on either side of the "demarcation line" between discoloured and normally coloured areas of traumatized muscle tissue. Anaesthetized pigs were injured in one thigh with a high velocity spherical steel missile. The microcirculatory flow of the traumatized muscle was studied by measuring the clearance of 133Xenon from the surface of the muscle and tissue oxygen pressure (PtO2) was measured with an MDO electrode. Measurements were done before and 1, 3 and 5 hours after the trauma. A markedly decreased or absent flow as well as very low PtO2 values were found within areas of discolouration. In the adjacent normally coloured areas no such changes were noted and the values of these areas resembled those of the contralateral untraumatized leg. The results agree with those of earlier studies of circulation and metabolic changes indicating that discolouration is a useful sign in the clinical assessment of muscle viability after high-energy trauma.